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I'm a PHP developer. I like PHP! It is a really good language if you know how to use it, but I know it allows very bad design sometimes.
It reminds me of JavaScript which has good parts and bad parts. One particular project, CoffeeScript, tries to focus only on the good parts, forcing you to write good code.
I was thinking if something similar could be done with PHP... A new syntax that would be compiled only to good PHP code taking advatage of all the new and exciting stuff we can get with PHP 5.3.
So, getting ahead of some people, I'll ask: Why create a new language on top of PHP if you can just use Ruby or Python or something else?
PHP is easy to deploy anywhere
The language itself has a lot of good features and ideas
There are lots of good libraries written in PHP
...
So, my real questions here are...
Is this a stupid idea? Why would it be? Do you think CoffeeScript is stupid?
How do someone starts to create a new language on top of another? I know nothing about this, but I would like to learn. Where to start?
The idea is definitely not stupid, especially if executed well.
I like coffeescript a lot, but it has it's approach has downsides as well. Debugging a coffeescript script still requires you read the generated Javascript code, which can be tedious, since you haven't written it actually yourself.
I've understood that Jeremy Ashkenas, the creator of coffeescript has started to work on coffeescript after reading "Create your own freaking awesome programming language" by Marc-André Cournoyer.
Good luck!
The reason CoffeScript is a good idea is that if developers want to run code in a client browser they have to use javascript; so the only way to program in a different language is to allow that language to be convertible to javascript.
I'm not sure the same really applies to server side programming. If you've got issues with PHP and want to use a new language there is no real advantage to having that language generate PHP.
On the other hand, a language that was very similar to PHP, but fixed some of the flaws would be a great idea.
Heh, great idea. My thoughts, some contradictory...
There are precedents for civilizing bad languages by putting syntax preprocessors in front of them.
In the early days of Unix, Fortran was popular and about the only portable language because most machines had no C compiler. But the vanilla Fortran of the day didn't even have block structured if-then-else, just a goofy single-statement if or an if-goto. So, the Ratfor language was implemented as a preprocessor for Fortran-66.
I believe there were (are?) Cobol preprocessors that presumably dealt with the verbosity and limitations of early Cobol dialects.
To this day Unix-derived systems ship with a macro processor called m4.
Several CSS preprocessors are available today, most notably Sass and LESS.
But...
Just let it die, and the sooner the better
The problem isn't really in the syntax.
I don't see much of a JavaScript-PHP parallel. JavaScript is a great language. It's kind of the opposite of PHP.
I'm not sure why you say that PHP is a great language. It's one of the worst. Every decent feature is a patch or repatch in a recent version.
As you noted, there is a fixed-up version of PHP already: it's called Ruby and, as a language, it's near-perfect. There is another fixed-up version called Python. The world would be better off in the long run if we support the better systems.
It is here now. A new language which is to PHP what CoffeeScript is to Javascript. (I.e., awesome.)
SNOWSCRIPT
Snowscript code looks like this:
fn how_big_is_it(number)
if number < 100
<- "small"
else
<- "big"
PHP output looks like this:
function how_big_is_it($number) {
if ($number < 100) {
return "small";
} else {
return "big";
}
}
All it needs now, is you.
If it would be to PHP what something like sass is to CSS, I'd be interested. But what would exactly would you want to add? Or would you just want to weed out the bad?
And what would you consider to be the bad?
Writing a PHP syntax transformer would probably be a neat project.
However, don't forget that PHP's standard library is a huge mess. Cleaning that up, would be a far bigger task.
The more I am thinking about this, the more irrealistic it sounds. The reason is simple: There actually are such language proprocessors already. Two of them (though not using PHP as implementation, only as compilation target) can be found here. But simply nobody uses them.
Yes, if the compiler itself were written in PHP, probably more people would use it. But I really can't see a way how to get this popular enough to be worth the work.
Another big problem is, that people mostly are used to their awesome code-highlighting, code-completing, code-inspecting IDE. Without getting IDE support probably merely anybody will use it (and IDE support can only be obtained by having many people use it...)
Thoughts?
I can see writing compilers to JavaScript (because the web imposes it upon us), but this sounds like a waste of time.
Haxe already does this, although it's not specifically targeted at PHP (linked to the Wikipedia article instead of their website because I'm afraid I'm going to get exploited if I visit the real site...)
PHP is easy to deploy anywhere
...as are its vulnerabilities.
I know it allows very bad design sometimes.
That's a bit of an understatement, it doesn't even have a module system, has no encapsulation, and has tons of silly things such as dynamic name resolution.
PHP is slow enough as it is, do you really want something an order of a magnitude slower?
Java is much more easy to deploy anyways, and lets you drop down to the bytecode level if you want. Java also gives you access to moderately sane libraries.
This is something I have thought about already often. PHP just is messy at some points.
Actually, I already have a project PrePHP focusing on providing PHP 5.3 functionality to PHP 5.2. But it adds some minor language features, like func()[0]. I haven't developed this project for some time and it definitely isn't "clean", but it shows, that what you want is possible and actually even not that complicated.
If you are serious about this, I am perfectly willing to collaborate with you.
Very interesting idea and if it come to life i think that i wan't to be involved in :)
For start You may check and read this position http://www.amazon.com/Masterminds-Programming-Conversations-Creators-Languages/dp/0596515170 (iam reading it now). It makes clear how really complicated is to maintain own language.
I agree that PHP definitely could do with some improvement, right now it allows for too much fooling around.
Some things I'd like to see
Static Typing
Required indentation
Proper use of objects (using arrays as objects is just stupid)
Then again, maybe I should just drop PHP and start working with Ruby or Python.
I'm like 8 years too late, but I'll answer anyways for anyone else who stumbles upon this.
Hack is a language developed by Facebook to deal with some of the issues of PHP, since Facebook had a large PHP codebase. Hack adds some nice features on top of PHP such as gradual typing (what TypeScript has) and generics, among other features, and gets rid of some of the more dangerous PHP features. Hack was at one point a superset of PHP, but is no longer completely compatible after removing some of the worse PHP features.
This is slightly different from what you were asking, since at this point Hack has its own interpreter, written by Facebook, but this started out as "better language that compiles to PHP", so I thought it was worth mentioning here.
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I am setting out to do a side project that has the goal of translating code from one programming language to another. The languages I am starting with are PHP and Python (Python to PHP should be easier to start with), but ideally I would be able to add other languages with (relative) ease. The plan is:
This is geared towards web development. The original and target code will be be sitting on top of frameworks (which I will also have to write). These frameworks will embrace an MVC design pattern and follow strict coding conventions. This should make translation somewhat easier.
I am also looking at IOC and dependency injection, as they might make the translation process easier and less error prone.
I'll make use of Python's parser module, which lets me fiddle with the Abstract Syntax Tree. Apparently the closest I can get with PHP is token_get_all(), which is a start.
From then on I can build the AST, symbol tables and control flow.
Then I believe I can start outputting code. I don't need a perfect translation. I'll still have to review the generated code and fix problems. Ideally the translator should flag problematic translations.
Before you ask "What the hell is the point of this?" The answer is... It'll be an interesting learning experience. If you have any insights on how to make this less daunting, please let me know.
EDIT:
I am more interested in knowing what kinds of patterns I could enforce on the code to make it easier to translate (ie: IoC, SOA ?) the code than how to do the translation.
I've been building tools (DMS Software Reengineering Toolkit) to do general purpose program manipulation (with language translation being a special case) since 1995, supported by a strong team of computer scientists. DMS provides generic parsing, AST building, symbol tables, control and data flow analysis, application of translation rules, regeneration of source text with comments, etc., all parameterized by explicit definitions of computer languages.
The amount of machinery you need to do this well is vast (especially if you want to be able to do this for multiple languages in a general way), and then you need reliable parsers for languages with unreliable definitions (PHP is perfect example of this).
There's nothing wrong with you thinking about building a language-to-language translator or attempting it, but I think you'll find this a much bigger task for real languages than you expect. We have some 100 man-years invested in just DMS, and another 6-12 months in each "reliable" language definition (including the one we painfully built for PHP), much more for nasty languages such as C++. It will be a "hell of a learning experience"; it has been for us. (You might find the technical Papers section at the above website interesting to jump start that learning).
People often attempt to build some kind of generalized machinery by starting with some piece of technology with which they are familiar, that does a part of the job. (Python ASTs are great example). The good news, is that part of the job is done. The bad news is that machinery has a zillion assumptions built into it, most of which you won't discover until you try to wrestle it into doing something else. At that point you find out the machinery is wired to do what it originally does, and will really, really resist your attempt to make it do something else. (I suspect trying to get the Python AST to model PHP is going to be a lot of fun).
The reason I started to build DMS originally was to build foundations that had very few such assumptions built in. It has some that give us headaches. So far, no black holes. (The hardest part of my job over the last 15 years is to try to prevent such assumptions from creeping in).
Lots of folks also make the mistake of assuming that if they can parse (and perhaps get an AST), they are well on the way to doing something complicated. One of the hard lessons is that you need symbol tables and flow analysis to do good program analysis or transformation. ASTs are necessary but not sufficient. This is the reason that Aho&Ullman's compiler book doesn't stop at chapter 2. (The OP has this right in that he is planning to build additional machinery beyond the AST). For more on this topic, see Life After Parsing.
The remark about "I don't need a perfect translation" is troublesome. What weak translators do is convert the "easy" 80% of the code, leaving the hard 20% to do by hand. If the application you intend to convert are pretty small, and you only intend to convert it once well, then that 20% is OK. If you want to convert many applications (or even the same one with minor changes over time), this is not nice. If you attempt to convert 100K SLOC then 20% is 20,000 original lines of code that are hard to translate, understand and modify in the context of another 80,000 lines of translated program you already don't understand. That takes a huge amount of effort. At the million line level, this is simply impossible in practice. (Amazingly there are people that distrust automated tools and insist on translating million line systems by hand; that's even harder and they normally find out painfully with long time delays, high costs and often outright failure.)
What you have to shoot for to translate large-scale systems is high nineties percentage conversion rates, or it is likely that you can't complete the manual part of the translation activity.
Another key consideration is size of code to be translated. It takes a lot of energy to build a working, robust translator, even with good tools. While it seems sexy and cool to build a translator instead of simply doing a manual conversion, for small code bases (e.g., up to about 100K SLOC in our experience) the economics simply don't justify it. Nobody likes this answer, but if you really have to translate just 10K SLOC of code, you are probably better off just biting the bullet and doing it. And yes, that's painful.
I consider our tools to be extremely good (but then, I'm pretty biased). And it is still very hard to build a good translator; it takes us about 1.5-2 man-years and we know how to use our tools. The difference is that with this much machinery, we succeed considerably more often than we fail.
My answer will address the specific task of parsing Python in order to translate it to another language, and not the higher-level aspects which Ira addressed well in his answer.
In short: do not use the parser module, there's an easier way.
The ast module, available since Python 2.6 is much more suitable for your needs, since it gives you a ready-made AST to work with. I've written an article on this last year, but in short, use the parse method of ast to parse Python source code into an AST. The parser module will give you a parse tree, not an AST. Be wary of the difference.
Now, since Python's ASTs are quite detailed, given an AST the front-end job isn't terribly hard. I suppose you can have a simple prototype for some parts of the functionality ready quite quickly. However, getting to a complete solution will take more time, mainly because the semantics of the languages are different. A simple subset of the language (functions, basic types and so on) can be readily translated, but once you get into the more complex layers, you'll need heavy machinery to emulate one language's core in another. For example consider Python's generators and list comprehensions which don't exist in PHP (to my best knowledge, which is admittedly poor when PHP is involved).
To give you one final tip, consider the 2to3 tool created by the Python devs to translate Python 2 code to Python 3 code. Front-end-wise, it has most of the elements you need to translate Python to something. However, since the cores of Python 2 and 3 are similar, no emulation machinery is required there.
Writing a translator isn't impossible, especially considering that Joel's Intern did it over a summer.
If you want to do one language, it's easy. If you want to do more, it's a little more difficult, but not too much. The hardest part is that, while any turing complete language can do what another turing complete language does, built-in data types can change what a language does phenomenally.
For instance:
word = 'This is not a word'
print word[::-2]
takes a lot of C++ code to duplicate (ok, well you can do it fairly short with some looping constructs, but still).
That's a bit of an aside, I guess.
Have you ever written a tokenizer/parser based on a language grammar? You'll probably want to learn how to do that if you haven't, because that's the main part of this project. What I would do is come up with a basic Turing complete syntax - something fairly similar to Python bytecode. Then you create a lexer/parser that takes a language grammar (perhaps using BNF), and based on the grammar, compiles the language into your intermediate language. Then what you'll want to do is do the reverse - create a parser from your language into target languages based on the grammar.
The most obvious problem I see is that at first you'll probably create horribly inefficient code, especially in more powerful* languages like Python.
But if you do it this way then you'll probably be able to figure out ways to optimize the output as you go along. To summarize:
read provided grammar
compile program into intermediate (but also Turing complete) syntax
compile intermediate program into final language (based on provided grammar)
...?
Profit!(?)
*by powerful I mean that this takes 4 lines:
myinput = raw_input("Enter something: ")
print myinput.replace('a', 'A')
print sum(ord(c) for c in myinput)
print myinput[::-1]
Show me another language that can do something like that in 4 lines, and I'll show you a language that's as powerful as Python.
There are a couple answers telling you not to bother. Well, how helpful is that? You want to learn? You can learn. This is compilation. It just so happens that your target language isn't machine code, but another high-level language. This is done all the time.
There's a relatively easy way to get started. First, go get http://sourceforge.net/projects/lime-php/ (if you want to work in PHP) or some such and go through the example code. Next, you can write a lexical analyzer using a sequence of regular expressions and feed tokens to the parser you generate. Your semantic actions can either output code directly in another language or build up some data structure (think objects, man) that you can massage and traverse to generate output code.
You're lucky with PHP and Python because in many respects they are the same language as each other, but with different syntax. The hard part is getting over the semantic differences between the grammar forms and data structures. For example, Python has lists and dictionaries, while PHP only has assoc arrays.
The "learner" approach is to build something that works OK for a restricted subset of the language (such as only print statements, simple math, and variable assignment), and then progressively remove limitations. That's basically what the "big" guys in the field all did.
Oh, and since you don't have static types in Python, it might be best to write and rely on PHP functions like "python_add" which adds numbers, strings, or objects according to the way Python does it.
Obviously, this can get much bigger if you let it.
I will second #EliBendersky point of view regarding using ast.parse instead of parser (which I did not know about before). I also warmly recommend you to review his blog. I used ast.parse to do Python->JavaScript translator (#https://bitbucket.org/amirouche/pythonium). I've come up with Pythonium design by somewhat reviewing other implementations and trying them on my own. I forked Pythonium from https://github.com/PythonJS/PythonJS which I also started, It's actually a complete rewrite . The overall design is inspired from PyPy and http://www.hpl.hp.com/techreports/Compaq-DEC/WRL-89-1.pdf paper.
Everything I tried, from beginning to the best solution, even if it looks like Pythonium marketing it really isn't (don't hesitate to tell me if something doesn't seem correct to the netiquette):
Implement Python semantic in Plain Old JavaScript using prototype inheritance: AFAIK it's impossible to implement Python multiple inheritance using JS prototype object system. I did try to do it using other tricks later (cf. getattribute). As far as I know there is no implementation of Python multiple inheritance in JavaScript, the best that exists is Single inhertance + mixins and I'm not sure they handle diamond inheritance. Kind of similar to Skulpt but without google clojure.
I tried with Google clojure, just like Skulpt (compiler) instead of actually reading Skulpt code #fail. Anyway because of JS prototype based object system still impossible. Creating binding was very very difficult, you need to write JavaScript and a lot of boilerplate code (cf. https://github.com/skulpt/skulpt/issues/50 where I am the ghost). At that time there was no clear way to integrate the binding in the build system. I think that Skulpt is a library and you just have to include your .py files in the html to be executed, no compilation phase required to be done by the developer.
Tried pyjaco (compiler) but creating bindings (calling Javascript code from Python code) was very difficult, there was too much boilerplate code to create every time. Now I think pyjaco is the one that more near Pythonium. pyjaco is written in Python (ast.parse too) but a lot is written in JavaScript and it use prototype inheritance.
I never actually succeed at running Pyjamas #fail and never tried to read the code #fail again. But in my mind PyJamas was doing API->API tranlation (or framework to framework) and not Python to JavaScript translation. The JavaScript framework consume data that is already in the page or data from the server. Python code is only "plumbing". After that I discovered that pyjamas was actually a real python->js translator.
Still I think it's possible to do API->API (or framework->framework) translation and that's basicly what I do in Pythonium but at lower level. Probably Pyjamas use the same algorithm as Pythonium...
Then I discovered brython fully written in Javascript like Skulpt, no need for compilation and lot of fluff... but written in JavaScript.
Since the initial line written in the course of this project, I knew about PyPy, even the JavaScript backend for PyPy. Yep, you can, if you find it, directly generate a Python interpreter in JavaScript from PyPy. People say, it was a disaster. I read no where why. But I think the reason is that the intermediate language they use to implement the interpreter, RPython, is a subset of Python tailored to be translated to C (and maybe asm). Ira Baxter says you always make assumptions when you build something and probably you fine tune it to be the best at what it's meant to do in the case of PyPy: Python->C translation. Those assumptions might not be relevant in another context worse they can infere overhead otherwise said direct translation will most likely always be better.
Having the interpreter written in Python sounded like a (very) good idea. But I was more interested in a compiler for performance reasons also it's actually more easy to compile Python to JavaScript than interpret it.
I started PythonJS with the idea of putting together a subset of Python that I could easily translate to JavaScript. At first I didn't even bother to implement OO system because of past experience. The subset of Python that I achieved to translate to JavaScript are:
function with full parameters semantic both in definition and calling. This is the part I am most proud of.
while/if/elif/else
Python types were converted to JavaScript types (there is no python types of any kind)
for could iterate over Javascript arrays only (for a in array)
Transparent access to JavaScript: if you write Array in the Python code it will be translated to Array in javascript. This is the biggest achievement in terms of usability over its competitors.
You can pass function defined in Python source to javascript functions. Default arguments will be taken into account.
It add has special function called new which is translated to JavaScript new e.g: new(Python)(1, 2, spam, "egg") is translated to "new Python(1, 2, spam, "egg").
"var" are automatically handled by the translator. (very nice finding from Brett (PythonJS contributor).
global keyword
closures
lambdas
list comprehensions
imports are supported via requirejs
single class inheritance + mixin via classyjs
This seems like a lot but actually very narrow compared to full blown semantic of Python. It's really JavaScript with a Python syntax.
The generated JS is perfect ie. there is no overhead, it can not be improved in terms of performance by further editing it. If you can improve the generated code, you can do it from the Python source file too. Also, the compiler did not rely on any JS tricks that you can find in .js written by http://superherojs.com/, so it's very readable.
The direct descendant of this part of PythonJS is the Pythonium Veloce mode. The full implementation can be found # https://bitbucket.org/amirouche/pythonium/src/33898da731ee2d768ced392f1c369afd746c25d7/pythonium/veloce/veloce.py?at=master 793 SLOC + around 100 SLOC of shared code with the other translator.
An adapted version of pystones.py can be translated in Veloce mode cf. https://bitbucket.org/amirouche/pythonium/src/33898da731ee2d768ced392f1c369afd746c25d7/pystone/?at=master
After having setup basic Python->JavaScript translation I choosed another path to translate full Python to JavaScript. The way of glib doing object oriented class based code except the target language is JS so you have access to arrays, map-like objects and many other tricks and all that part was written in Python. IIRC there is no javascript code written by in Pythonium translator. Getting single inheritance is not difficult here are the difficult parts making Pythonium fully compliant with Python:
spam.egg in Python is always translated to getattribute(spam, "egg") I did not profile this in particular but I think that where it loose a lot of time and I'm not sure I can improve upon it with asm.js or anything else.
method resolution order: even with the algorithm written in Python, translating it to Python Veloce compatible code was a big endeavour.
getattributre: the actual getattribute resolution algorithm is kind of tricky and it still doesn't support data descriptors
metaclass class based: I know where to plug the code, but still...
last bu not least: some_callable(...) is always transalted to "call(some_callable)". AFAIK the translator doesn't use inference at all, so every time you do a call you need to check which kind of object it is to call it they way it's meant to be called.
This part is factored in https://bitbucket.org/amirouche/pythonium/src/33898da731ee2d768ced392f1c369afd746c25d7/pythonium/compliant/runtime.py?at=master It's written in Python compatible with Python Veloce.
The actual compliant translator https://bitbucket.org/amirouche/pythonium/src/33898da731ee2d768ced392f1c369afd746c25d7/pythonium/compliant/compliant.py?at=master doesn't generate JavaScript code directly and most importantly doesn't do ast->ast transformation. I tried the ast->ast thing and ast even if nicer than cst is not nice to work with even with ast.NodeTransformer and more importantly I don't need to do ast->ast.
Doing python ast to python ast in my case at least would maybe be a performance improvement since I sometime inspect the content of a block before generating the code associated with it, for instance:
var/global: to be able to var something I must know what I need to and not to var. Instead of generating a block tracking which variable are created in a given block and inserting it on top of the generated function block I just look for revelant variable assignation when I enter the block before actually visiting the child node to generate the associated code.
yield, generators have, as of yet, a special syntax in JS, so I need to know which Python function is a generator when I want to write the "var my_generator = function"
So I don't really visit each node once for each phase of the translation.
The overall process can be described as:
Python source code -> Python ast -> Python source code compatible with Veloce mode -> Python ast -> JavaScript source code
Python builtins are written in Python code (!), IIRC there is a few restrictions related to bootstraping types, but you have access to everything that can translate Pythonium in compliant mode. Have a look at https://bitbucket.org/amirouche/pythonium/src/33898da731ee2d768ced392f1c369afd746c25d7/pythonium/compliant/builtins/?at=master
Reading JS code generated from pythonium compliant can be understood but source maps will greatly help.
The valuable advice I can give you in the light of this experience are kind old farts:
extensively review the subject both in literature and existing projects closed source or free. When I reviewed the different existing projects I should have given it way more time and motivation.
ask questions! If I knew beforehand that PyPy backend was useless because of the overhead due to C/Javascript semantic mismatch. I would maybe had Pythonium idea way before 6 month ago maybe 3 years ago.
know what you want to do, have a target. For this project I had different objectives: pratice a bit a javascript, learn more of Python and be able to write Python code that would run in the browser (more and that below).
failure is experience
a small step is a step
start small
dream big
do demos
iterate
With Python Veloce mode only, I'm very happy! But along the way I discovered that what I was really looking for was liberating me and others from Javascript but more importantly being able to create in a comfortable way. This lead me to Scheme, DSL, Models and eventually domain specific models (cf. http://dsmforum.org/).
About what Ira Baxter response:
The estimations are not helpful at all. I took me more or less 6 month of free time for both PythonJS and Pythonium. So I can expect more from full time 6 month. I think we all know what 100 man-year in an enterprise context can mean and not mean at all...
When someone says something is hard or more often impossible, I answer that "it only takes time to find a solution for a problem that is impossible" otherwise said nothing is impossible except if it's proven impossible in this case a math proof...
If it's not proven impossible then it leaves room for imagination:
finding a proof proving it's impossible
and
If it is impossible there may be an "inferior" problem that can have a solution.
or
if it's not impossible, finding a solution
It's not just optimistic thinking. When I started Python->Javascript everybody was saying it was impossible. PyPy impossible. Metaclasses too hard. etc... I think that the only revolution that brings PyPy over Scheme->C paper (which is 25 years old) is some automatic JIT generation (based hints written in the RPython interpreter I think).
Most people that say that a thing is "hard" or "impossible" don't provide the reasons. C++ is hard to parse? I know that, still they are (free) C++ parser. Evil is in the detail? I know that. Saying it's impossible alone is not helpful, It's even worse than "not helpful" it's discouraging, and some people mean to discourage others. I heard about this question via https://stackoverflow.com/questions/22621164/how-to-automatically-generate-a-parser-code-to-code-translator-from-a-corpus.
What would be perfection for you? That's how you define next goal and maybe reach the overall goal.
I am more interested in knowing what kinds of patterns I could enforce
on the code to make it easier to translate (ie: IoC, SOA ?) the code
than how to do the translation.
I see no patterns that can not be translated from one language to another language at least in a less than perfect way. Since language to language translation is possible, you'd better aim for this first. Since, I think according to http://en.wikipedia.org/wiki/Graph_isomorphism_problem, translation between two computer languages is a tree or DAG isomorphism. Even if we already know that they are both turing complete, so...
Framework->Framework which I better visualize as API->API translation might still be something that you might keep in mind as a way to improve the generated code. E.g: Prolog as very specific syntax but still you can do Prolog like computation by describing the same graph in Python... If I was to implement a Prolog to Python translator I wouldn't implement unification in Python but in a C library and come up with a "Python syntax" that is very readable for a Pythonist. In the end, syntax is only "painting" for which we give a meaning (that's why I started scheme). Evil is in the detail of the language and I'm not talking about the syntax. The concepts that are used in the language getattribute hook (you can live without it) but required VM features like tail-recursion optimisation can be difficult to deal with. You don't care if the initial program doesn't use tail recursion and even if there is no tail recursion in the target language you can emulate it using greenlets/event loop.
For target and source languages, look for:
Big and specific ideas
Tiny and common shared ideas
From this will emerge:
Things that are easy to translate
Things that are difficult to translate
You will also probably be able to know what will be translated to fast and slow code.
There is also the question of the stdlib or any library but there is no clear answer, it depends of your goals.
Idiomatic code or readable generated code have also solutions...
Targeting a platform like PHP is much more easy than targeting browsers since you can provide C-implementation of slow and/or critical path.
Given you first project is translating Python to PHP, at least for the PHP3 subset I know of, customising veloce.py is your best bet. If you can implement veloce.py for PHP then probably you will be able to run the compliant mode... Also if you can translate PHP to the subset of PHP you can generate with php_veloce.py it means that you can translate PHP to the subset of Python that veloce.py can consume which would mean that you can translate PHP to Javascript. Just saying...
You can also have a look at those libraries:
https://bitbucket.org/logilab/astroid
https://bitbucket.org/logilab/pylint-brain
Also you might be interested by this blog post (and comments): https://www.rfk.id.au/blog/entry/pypy-js-poc-jit/
This Google Tech Talk from Ira Baxter is interesting https://www.youtube.com/watch?v=C-_dw9iEzhA
You could take a look at the Vala compiler, which translates Vala (a C#-like language) into C.
I'm going to be starting a fairly large PHP application this summer, on which I'll be the sole developer (so I don't have any coding conventions to conform to aside from my own).
PHP 5.3 is a decent language IMO, despite the stupid namespace token. But one thing that has always bothered me about it is the standard library and its lack of a naming convention.
So I'm curious, would it be seriously bad practice to wrap some of the most common standard library functions in my own functions/classes to make the names a little better? I suppose it could also add or modify some functionality in some cases, although at the moment I don't have any examples (I figure I will find ways to make them OO or make them work a little differently while I am working).
If you saw a PHP developer do this, would you think "Man, this is one shoddy developer?"
Additionally, I don't know much (or anything) about if/how PHP is optimized, and I know that usually PHP performace doesn't matter. But would doing something like this have a noticeable impact on the performance of my application?
You might be the only developer now but will someone else ever pick up this code? If so you really should stick mainly to the standard library names if you're doing nothing more than simply wrapping the call.
I've worked with code where the author has wrapped calls like this and it really does harm the ability to quickly understand the code
If you saw a PHP developer do this, would you think "Man, this is one shoddy developer?"
Well no...but I'd think "Damn...I've got to learn this guys new naming standard which although well-intentioned will take me time"
I assume you are referring not only to naming conventions, but also to the merry mixture of function (needle, haystack) and function(haystack, needle) parameter orders.
I can totally understand the desire to build sane wrappers around these in self-defense. I still rather wouldn't do it, though, simply because it adds a proprietary layer to your project that will make it harder to understand for others. Everybody knows what array_push does, but MyArrayFunctions::push one may have to look up, or even look into to find out what it does.
I tend to stick with the standards, even though they're admittedly crappy in this case. Plus, with a decent IDE that can look up functions and parameters as you type, the problem is already much reduced.
On the other hand, I can't really see any harm in, say, a static class Array that brings all the push(), pop(), array_this() and array_that() into one standard form. I'd say it's up to you, really.
Simple wrappers wont hit your performance, but this might confuse any future developers on the project. As a PHP programmer you slowly come to expect the weird naming conventions.
If you are adding any functionality its great to have consistent conventions. I have worked with a PHP static class that did wrap the native array functions (and add new ones). It was quite convenient to always have the same argument placements.
In my opinion OOP implementations of for example an array are okay, you will wrap them and partially modify functionality, however just renaming functions and shuffling arguments I don't like.
If you really need to do it make sure you comment it with phpdoc so people can see the correct syntax in the autocomplete of their IDE.
Somebody said that when your PHP code and application use global variables then it must be spaghetti code (I assume this). I use WordPress a lot. As far as I know, it's the best thing near great PHP software. And it uses many global variables to interact between its components.
But forget about that, because frankly, that's the only thing I know. So it's completely biased ;D
So, I am just curious, What is the characteristic of spaghetti code?
PS: the only thing I know is WordPress. So, hopefully, maybe this will help somebody give a great answer for somebody who has little experience in developing a full web application on PHP (for example, the Stack Overflow website).
No modularity (everything in one file, class, module, namespace, package, or whatever your language uses to provide modularity),
Plenty of goto's,
Poor organization,
No clear separation of functionality and purpose. (That is, all-encompassing classes or functions)
Long functions.
Poor naming.
No consistent coding style throughout.
No clear interface contract between implementation and clients of code. (That is, no specification of what the inputs, outputs, pre- and post-conditions of functions are)
Over-reliance on internals of data structures with little abstraction.
Functions randomly permute/modify global state without any mention of it in documentation.
Lack of comments or documentation of non-trivial code.
Code that is more complicated than it needs to be.
Lack of reuse. (plenty of duplicated code, a.k.a. copypasta)
No verification or unit testing (it works on faith).
Magic numbers.
In essence, a lack of design and
forethought, and just a mishmash of
hacks slapped together. This applies to any language, not just PHP.
for somebody who has little experience in developing a full web application on PHP (for example, the Stack Overflow website)
Just FYI, but Stack Overflow was not developed with PHP.
Well, talking of comment you posted, the explanation is very simple.
Using global operator makes source of a variable is unknown, like other end of spaghetti noodle. It can be defined everywhere. So, when you call your function, you have no idea what value this variable has. Instead of it, direct passing a variable makes it plain and clear:
function hello_testing($conditional_random) {
if ($conditional_random)) {
echo "foo is inside";
}
}
P.S. http://en.wikipedia.org/wiki/Spaghetti_code
Spaghetti code has specific characteristics which distinguish it from plain poor code. Spaghetti is extremely complicated and unstructured, so it is hard to follow the flow of a process through the program. It is like trying to untangle the noodles in a bowl of bolognese.
This is why GOTO statements (dread word!) are often cited in this context: a GOTO statement transfers control to another arbitrarily defined location in the code base. Most programming languages have commands which can be abused to simulate goto style behaviour; for instance, using exceptions to implement regular business logic rather than handling errors.
Global variables contribute to spaghetti code because the values are assigned outside of the scope of the current program unit. This can make it difficult to determine where in the code base a variable is set to a given value (or indeed whether it is set to any value at all).
Spaghetti code can be functionally correct and performative. It's a problem because it's hard to understand, so we can't be sure it is bug free and the lack of structure makes it difficult to troubleshoot. For similar reasons spaghetti code is brittle and difficult to change; the risk of introducing a bug is high.
Incidentally, the use of goto statements does not mean a program is spaghetti. It is perfectly possible to write clear, well-structured code using goto, it is just requires a lot of self-discipline not to abuse its flexibility. Modern programming languages have made its use unnecessary, and undesirable.
WordPress is the biggest piece of spaghetti code PHP I have seen around. There is a shocking mix of PHP, HTML, JavaScript and all things in between all lumped in the same files. If you want another example of spaghetti code look at osCommerce or Zen Cart.
In fact I dare say a large majority of open source PHP applications are pretty shocking examples of how to program in PHP. If you want to look at a good structured example (that is, non-spaghetti) then look at Yii framework or Zend Framework. Frameworks like CodeIgniter and Kohana, although not spaghetti, are not very good examples of how to structure things in PHP 5 as they use many of the features used in PHP 4 simply because there was no better way of doing them until PHP 5 (for example, using path based inheritance instead of true object inheritance).
If you want a reasonbly good example of procedural programming done right look at Drupal. It might not be the best performing PHP application, because of the complexity, but it sure beats WordPress and you can do many of the same things with it.
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I would like to be a PHP/MySQL programmer
What are the technologies that I must know?
Like:
Frameworks
IDEs
Template Engines
Ajax and CSS Frameworks
Please tell me the minimum requirements that I must know, and tell me your favourite things in the previous list?
Thanks
First off, there is no must know about learning PHP and MySQL... You go into it not knowing anything, and you'll come out of it knowing a bunch. If there was a must know, then nobody would be able to get into PHP and MySQL development. I personally think you are at a slight advantage going into this without knowing everything about it. It'll give you a fresh perspective and a think outside of the box attitude :)
As far as the object oriented stuff in this thread, it's true. But, as others have said, it's completely up to the programmer (you) to decide how to write your code. You can use object oriented practices, make a spaghetti code junction, or just right a bunch of functions, or whatever. Either way, as everyone else has been saying, it's up to you :)
IRC channel:
Don't really need this, but I find it helpful... See you in here :)
irc.freenode.net #php
Manual:
The manual is your friend and probably the only thing you should know before diving in.
http://www.php.net/manual/en/
http://dev.mysql.com/doc/refman/5.0/en/apis-php.html
Frameworks:
Make sure it's an MVC framework :)
http://www.cakephp.org/
http://www.phpmvc.net/
http://www.codeigniter.com/
http://www.symfony.com/
http://www.laravel.com
http://www.yiiframework.com/
IDE:
Whatever suits you best :)
http://www.eclipse.org/
http://www.vim.org/
http://www.zend.com/en/products/studio/
http://php.netbeans.org/
https://www.jetbrains.com/phpstorm/
Template engines:
PHP is a good template engine
Model view controller frameworks help with this
twig.sensiolabs.org
http://www.smarty.net/
Ajax:
http://jquery.com/
http://www.mootools.net/
http://developer.yahoo.com/yui/
http://www.prototypejs.org/
http://www.extjs.com/
http://code.google.com/webtoolkit/
https://angularjs.org/
CSS:
http://www.yaml.de/en/home.html
http://code.google.com/p/blueprintcss/
http://developer.yahoo.com/yui/reset/
Definitely not an exhaustive list, and things change constantly... But, it's a start :)
Have fun!
Chrelad
Security is an important topic every web programmer should study before being allowed to post code that can be accessed publicly on the internet.
Examples of security issues:
Injection flaws
Cross-site scripting flaws
Cross-site request forgery
There are more security issues that you should know and keep in mind as you write PHP applications. The website http://www.owasp.org contains lots of useful information to help.
PHP was my first language, which I learned on the side while working as an office junior in my first job over 10 years ago. Here is some things from my experience:
Download the PHP manual, print it off, and start reading from page one. Keep going till you're at the end. Skim over the bits you probably won't need (like using KADM5 or Hyperwave) but always read the introductions so you know what PHP is capable of (this will save you trying to re-invent the wheel). The PHP documentation blows the docs of pretty-much every other language I've worked with since out of the water.
Next step; set up PHP. Manually. Don't use XAMPP or anything else, do it yourself. It always helps to know how your environment is set up.
Don't bother with an IDE at the beginning. Getting to know a language means getting up-close-and-personal. IDEs obscure things in an attempt to help you GetThingsDone which works great when you know what you're doing and know your target environment, but when you're starting out they just get in the way and hide what's important.
Don't bother with frameworks at the beginning, either. Again, they're there to help you GetThingsDone which only works when you know what you're doing in the first place. Start with the basics, otherwise you'll be learning the framework and not PHP.
PHP is essentially an advanced templating engine. Don't fall into the trap of over-hyped "PHP templating engines". They're just doing what PHP already does, doubling-up on the work and running twice as slow as PHP does. Stick with inline html/php to start with. Again, this'll help you get to understand what PHP is, how it works, and when to use it.
As with AJAX and CSS... they're nothing to do with PHP, but with the output you produce from PHP (and with AJAX getting input in). Don't load your plate with too much to eat at once. Start with plain PHP+HTML, and do your CSS by hand. Then, when you're happy, mix in a little javascript.
The best thing you can do with any language is learn the environment you're going to be working in, because programming is (relatively) similar across all of them. They all have loops, data structures, input/output, etc, but they all work just that little differently.
Don't believe the hype. I'm moving from PHP to Python at the moment and I could've just jumped on the Django band-wagon to GetThingsDone, but I know that if I came across a problem I wouldn't know where to begin to fix it. So I'm taking my own advice and starting from the beginning; reading the manual, setting up an test system, parsing simple files, getting input/output, getting it linked in with a web server... all part of getting to know my new environment.
What should every PHP programmer know ?
You need to know a language that is not PHP. I'm not saying you shouldn't develop your sites in PHP, it's actually really good for that, but you really need to know at least one other language to get some perspective.
Why? PHP is broken and full of bad design and misfeatures. You can write excellent code in PHP, but you're never going to be able to spot the bad design and failures of PHP itself if you don't know any better.
I'd suggest python, ruby, or C#
PS: If you don't think this is a helpful suggestion, then by all means downmod this answer, but if you are downmodding because you feel insulted by my claim that PHP is broken and badly designed, don't shoot the messenger, I'm just telling the truth!
First of all, that PHP itself IS a templating system
Security.
Just like Lucas Oman said - it is up to you in PHP to write the code well; and it does not coddle you. If you don't understand why you need to confirm a logout, or why you can't just validate in javascript, or why register_globals is bad - your app will be vulnerable in some form or another.
You need to learn the following (I would suggest in this order):
Basic Object-Oriented Principles (such as inheritance, polymorphism, and encapsulation)
The PHP language itself. Specifically, PHP 5.
Database Design Principles such as tables, keys, relationships, normalization, etc.
SQL - Structured (or Standard never can remember which) Query Language. Specifically learn the basics of select, insert, update, and delete queries.
Good design principles and coding practices (you can find posts here on StackOverflow for one) such as dividing presentation and business logic.
A Framework, Any Framework - this will help you become introduced to more advanced concepts of object-oriented design patterns and allow you to follow tutorials that will encourage good design and coding practices.
Object-Oriented Design Patterns like MVC, Database Abstraction Models and the like
Advanced SQL and other database stuff like triggers, stored procedures, and other functions.
Ignore the mysql_* functions. Not only do they provide no straightforward method of writing secure code, they actually go out of their way to make it painful and tedious if you try. Use mysqli or PDO instead (and you've got no excuse now - PHP 4 was end-of-life'd months ago).
All good answers, but there is something important missing: If you want to seriously get into PHP, then you should be aware that there are a lot of PHP programmers out there who are lazy, inept, ignorant, misguided and unfortunately get their code released to the public. The history of PHP means that it supports some questionable features (not just things like register_globals but also smaller things like automatic initialization) and people still use them. You don't want to.
I would say the most important thing is to learn how the whole process of building a page with PHP works - in that requests come from a client (web browser), hit the web server, get passed through to PHP, which then generates the response that is sent back. A solid understanding of this will ground you in
why you can't send headers after output has started
how sessions and cookies work
how each page should be built in a stateless manner (i.e. deliver whatever the request asks for, don't remember what happened last time, or guess what the user is doing)
The difference between HTML, PHP, JavaScript and CSS, and more importantly, what each is used for primarily and where the responsibility of each lies.
Once you've got that down, then you should be quite comfortable with writing any app. But unless you've got that down, you'll start mixing things as I've seen many rookies do before now.
That every value everywhere has to be encoded appropriately. echo $some_variable_that_seems_innocent is evil nine times out of ten.
Use htmlspecialchars() in HTML/XML, prepared statements or at least addslashes() when building SQL queries, json_encode() when inserting values into scripts, rawurlencode() when appending URL components, escapeshellargs() when constructing shell commands, etc.
If you insert text in URL that's part of a script in XHTML document, you'll need to encode data three times.
Although this isn't a technology, I think it's very important that you understand that, when using PHP, it is completely on you to write good code. PHP is capable of it, but it does not encourage it. You are completely responsible for writing code that is well designed and, if you choose, follows OO principles. You will have no help from the language.
Use a great IDE (like Eclipse for example) that let you debug and have some code completion. This will save you some time.
PHP have a lot of programmer and is very popular = a lot of thing is already done for you, before writing some code, doing a google search is always a good idea.
You should use some of the Framework if you start from scratch. This will answer all your question about AJax, template engines... because most of them come with these packages.
Here is some post about how to start choosing a framework: SO 1, SO2, Here is a list of PHP Framework.
You can develop PHP on Windows, Linux or Mac.
Getting a web server setup
To run PHP and MySQL locally on your computer you will need to install Apache webserver with php module and MySQL database server. ie. a LAMP webserver (Linux Apache MySQL PHP).
In the past, I would recommend installing Ubuntu. These days, there are a few solutions available that will give you one click installation webserver without using linux.
For Windows:
http://www.wampserver.com
For OSX:
http://www.mamp.info
After having a LAMP webserver use w3schools.com tutorials to start.
I would say a basic one would be HTML. ;)
No Php framework expert.As templating which make the system much complex then as it.
Understand business logic requirement and think the cons/pro.Hoping for SA to think all for you is not good programmer.
No ajax.I dealing with large of data,rendering to one js file about 4000 k data is very bad.
Start from notepad or VI
After learn php about 1 to 2 years,try learn other language like c# or c++ to improve your php application.
Php is addicted language rather then other language.You type it works.Other language,you type It's Compile It's Hang up.
7.For complexity application,php is the best to me rather then other language,because you think,you write it works.
You should know how to use effectively at least one Debugger/IDE. It is amazing what you can learn from your code by stepping through it and watching it run. It both makes it much simpler to track down bugs, and improves the quality of your code. I believe you should never commit code to a project that you haven't seen execute.
The PHP Language
Go to PHP.net and read through all of the documentation. When you are done, you won't know everything you need to know about php, but you will know where to look.
Be careful of code snippets you find on the web. Often they contain sql in html, which is bad practice, as well as security vulnerabilities such as sql injection. I've seen few that use prepared statements, which is good for security.
Personally, I found the book "Build your own database driven website using PHP and MySQL" extremely helpful.
Other than that, the one thing I found hardest to get used to with PHP is how relaxed it is, compared with any other language I've ever used. By that I mean no types, flexibility about syntax and punctuation. Personally I think that's a good thing, but I also know that it probably encourages pretty bad behavior.
Here's one other tip I have: try to use something like the DRY principle -- i.e., you'll find yourself writing the same little (or big) bits of code over and over again -- make them into functions as early as you can in the process of coding, and life will be a lot easier later on.