I need to understand how to load classes in php. I want to access classes methods by instantiate the class only with its name, for example:
$foo = new Foo();
$foo->method();
And not like this:
$foo = new \Class\Bar\Foo();
I'm in a Symfony 2.7 environment.
Thanks in advance!
EDIT
My bad, I should have specified that I'd like to use classes like this in the whole project, not only in a few files.
You should use those classes (i.e. import them) like:
use strrife\MyBundle\Entity as Entity;
...
$e = new Entity();
The official docs can be found here.
PS
If you're using some IDE (for example, PHPStorm which personally I highly recommend), then, when you type Entity and this class wasn't imported yet, it gives you a list of options to import that class from.
EDIT
You shouldn't do that.
Importing the classes like that in the entire project is actually a bad idea because that might cause naming conflicts (and probably will if you'd like to do that for Symfony classes).
As a workaround for your project classes you can add a few lines to composer.json specifying the autoload paths to all your project folders.
You can also:
put all your entities to one single folder (very bad)
or write a custom __autoload() function that would iterate through files and folders searching for your class (docs), but it'd bring the same problems + some performance issues.
But I highly discourage you from doing that because... well, namespaces bring order and structure and you're likely to end up with class redeclarations.
Related
I'm currently reading Modern PHP Book and I'm a little confused since in Chapter 2 the author talks about Namespace and he keeps saying import when he refers to the "use". In fact he states the following...
TIP
You should import code with the use keyword at the top
of each PHP file, immediately after the opening <?php tag or...
The way I understand Namespace is that the use keyword references the namespace of the class but it doesn't import it and you still need to use require or include to import the actual class, correct?
I'm I correct when I say that when using namespace without auto-loading you will need to use require or include to import your classes?
Thanks
If you use autoloader, such as composer, you do not need to import or require PHP files (you only load autoloader file, which actually does all that for you). If you have no autoloader, you have to load files using import or require.
Then, after FILE is loaded, you can use use statements to do actual work with name-spaced items, such as classes, interfaces or traits.
Yes, you're correct. The use keyword in PHP merely aliases a namespace, in that it does what a symlink (on a *nix system) or shortcut (on a Windows system) would.
If you read the manual about PHP namespace basics you'll see that namespaces can be analogous to a filesystem where class/interface/constant/function names can be divided up into folders in order to prevent name-clashes.
If you read the manual section on Namespace Importing you'll see that when we refer to importing in PHP it actually means to create a shortcut of one name to another name (in fact the shortcut analogy above is taken right from the manual)...
This is similar to the ability of unix-based filesystems to create symbolic links to a file or to a directory.
So, while confusing, the use keyword in PHP does not attempt to load (or include) the actual file containing the namespace, but rather just creates an alias for given namespace(s).
This may be very different use of the word import than you may be used to in other languages, where import can mean to load the actual file or package, but in PHP it's important to understand that importing a namespace has nothing to do with autoloading or including files. They are two separate concepts in PHP.
Importing a namespace is so that you can refer to \fully\qualified\namespace\MyClass as simply MyClass inside your namespace rather than having to use the FQN every single time (hence the shortcut analogy).
Autoloading, is for including the actual classes in PHP when they get used in code.
So there's a definite disconnect between the two concepts.
Since you mentioned a Chapter 2 in a book, I'm going to assume that you are still learning PHP, yes?
The use of use is to shorten namespaced classes to their root so that if you have some long namespaced class like
org\shared\axel\web\framework\connection\pipeline\impl\StopExecutionException
that needs to be instantiated with
new org\shared\axel\web\framework\connection\pipeline\impl\StopExecutionException();
You can use use to refer only to the root unnamespaced class
use org\shared\axel\web\framework\connection\pipeline\impl\StopExecutionException;
...
throw new StopExecutionException();
Keep in mind that you still need to have the class's code in your script, so you either include/require that manually by using include or require, or register autoloaders (see spl_autoload_register).
What that does is you define how your namespace maps to your source code's directory structure.
What others here refer to as composer is a package manager that includes an autoloader. At this stage, I personally think it's better to put off learning about this until you have a good grasp of the basics.
If you have an autoloader then use can be used to pull a Trait
Trait file
namespace Blah;
Trait Foo {
protected $somevar;
}
Class file
Class Bar {
use \Blah\Foo; // autoloaded
}
Otherwise, use is used to indicate that you want to either load a given class or alias that class as another
Class Foo {
}
use \Foo as Bar;
Class Something extends Bar {
}
I'm a beginner to L5. I read the documentation about extending classes but i didn't find any information about where to put the file in which i extend the class.
**I have to extend Str.php class. I have read that in L4 it had to be done by putting that file under App/folder but i didn't find that folder in L5.
So please can you tell me how can i do that?
This is the information i have now:
First, you must find where the class file is. We will be extending the Str class, which is under vendor/laravel/framework/src/Illuminate/Support. Note that you can also find this class under the aliases key in app/config/ app.php.
Now create a new folder called lib under app/folder. This folder will hold our class extensions. Because the Str class is grouped under the folder Support, it is suggested that you create a new folder named Support under lib too.
Now create a new file named Str.php under app/lib/Support, which you've just created:
But this is for L4
That's more of a general PHP question and there are two parts: 1) How to extend a class and 2) where to put files.
1) Extending classes isn't something Laravel or anyone else provides. That's right there in the language:
class A {}
class B extends A {}
As long as class A exists and is available, then class B can extend from it.
2) Where the files are is also important here. If you're defining class B and want to extend class A, the php runtime needs to know where to find A. Usually class A isn't defined in the same file as class B.
There are many ways to do this. You could require or include class A when you define class B. That would look something like:
a.php
class A {}
b.php
require "a.php";
class B extends A {}
Now with a lot of files like in the Laravel framework or any worthy library, you're going to have a lot of files to include and have to keep track of how to include those files. That's no fun. So, instead of doing that, PHP has provided a way to autoload the classes. That is, if you define classes in a predictable way, PHP can figure out what classes you're talking about without you having to use require or include statements.
There are also many ways of autoloading php files. In Laravel (and many, many other projects), the composer autoloader is used.
This means that files have to be placed in a pre-defined way in order for the composer autoloader to find them. By reading about the composer autoloader and then digging into the code to see how Laravel's classes are autoloaded, you'll be able to figure out how that happens.
Despite the intricate detail of Peter's answer, I figured I'd write something much more concrete: it doesn't matter.
If you check composer.json, you'll see that we are autoloading everything that is placed inside the app directory anyway. Hence, the choice is really yours. All that matters is that you maintain a sensible and readable structure. For example, you could place it in app/Lib, and namespace all your classes App\Lib (if App is your base namespace of course, which can be changed with php artisan app:name). Of course, you could also have a folder like Helpers/Lib for your extended classes, and keep some form of helpers.php with global helper functions in Helpers.
Why would you do this? Well, you might want to have an easy way to call your new Strfunctions, so instead of having to do Str::yourNewMethod($argument) everywhere, you could add a helper function yourMethod($argument) to easier call the function (if you intend to use it extensively).
One thing you have to remember though, as mentioned by Peter, is that the class you are extending won't automagically be found. It will, however, be autoloaded. Hence, to reference it you have to remember to namespace it, such as in the example below.
<?php namespace App\Helpers\Lib
Class Str extends \Illuminate\Support\Str {}
Also remember to namespace correctly when you call your own class.
Here is the scenario.
I am implementing namespaces into my projects.
I have my own custom bridge library that calls other libraries like Zend to do the heavy lifting.
I have no problem using fully qualified namespaces in my custom bridge library but would like to keep the code as terse as possible in my controllers, models and view.
Here is an example of some aliasses i would like to use:
use BridgeLibName\Stdlib\Arrays as arr;
use BridgeLibName\Stdlib\Objects as obj;
use BridgeLibName\Stdlib\Strings as str;
use BridgeLibName\Stdlib\Numbers as num;
use BridgeLibName\Stdlib\File as file;
etc.........
Example usage:
$file = new file('path/to/file.txt');
$file->create();
or
$obj = arr::toObject(['key1'=>'value1']);
is it possible in any way to create an alias or constant that can be globally accessible and not discarded at the end of each file?
Some kind of bootstrap file that can make these aliases stick.
As I was writing the question i thought of a solution.
You can fake it by creating classes that extend the namespaced classes.
example:
class arr extends BridgeLibName\Stdlib\Arrays{
}
One important thing to remember:
If you are going to extend the classes the namespaced class will have to be loaded.
This could have performance implications if used too much since aliases and namespaces are only loaded as needed.
Since I am only using it to bridge to other classes there is very little logic inside my bridge files.
These bridge files in turn uses aliases and namespaces correctly thus loading the real files as needed.
I you are not careful with the implementation you can load a lot of unnecessary stuff and cause your app to become slow and bloated.
A nice thing I noticed is that good IDEs like netbeans also seems to be able to do auto completion with this method.
If there is a better way to do this please let me know.
Just thought of an amendment to this method to fix the problem with unnecessary class instantiation.
The core library can work with the normal psr-0 loader.
To have the aliases autoload I created an aditional dir named includes next to my namespaced class.
in composer you describe it like so:
"autoload": {
"psr-0": {
"BridgeLibName\\": "."
},
"classmap": ["include/"]
}
Now your libraries will load as expected from the correct namespace and your alias classes will autoload as needed.
Classes put into the include dir can now extend the namespaced classes ( as shown above ) and will no longer be loaded prior to being used.
Now you have global aliases without having to sacrifice performance by loading unused classes.
basically, I have the following problem: I want to make use of PHP's new namespace features. Unfortunately, I'm running a PHP version (5.3.2) in which namespace-autoload-support for linux still seems buggy and does not work (PHP should be able to load the class file automatically by its namespace without having to use a custom autoloader, but that doesn't work).
What I want to achieve is to write an autoloader that I can simply remove as soon as the php's namespace features work correctly (there seems to be a speed advantage when not using a custom autoloader) with having to change as less code as possible afterwards.
So I have a call like this:
$filereader = new system\libraries\file\XML();
which gets passed correctly as the string "system\libraries\file\XML" to my autoload-function. I can load the corresponding file "system/libraries/file/XML.class.php". However, the class in there will be named
class XML { ... }
(or something different than "system\libraries\file\XML") and so have a different name than the one by which PHP will try to load it. So is there an easy way to load that class ("XML") which has a different name than the name which I pass to the autoloader function? Can I perhaps do something in the autoloader to achieve that behaviour? (I'm using spl_autoload_register).
I know that even if it worked out I would still not be able to use all features of namespacing, since a (simple) autoloader would not respect the "use namespace" directive and I would still have to use rather long names for loading a class. However, if I understood PHP's namespace-features correctly, I could leave the code as it is when I later switch to using native namespace support instead of my autoloader.
If what I try to do does not make sense at all in your opinion or if I misunderstood namespaces, please tell me (- I have not used PHP's namespace features yet).
I would load the file (which creates the XML class) and then alias the XML class to the properly namespaced system\libraries\file\XML class:
class_alias('XML', 'system\libraries\file\XML');
More generally:
class_alias(basename($class), $class));
Though I'm not quite sure whether class_alias can alias to namespaced classes...
In Codeigniter, when we use $this->load('class_name') in the controller, CI will try to create an instance of the class/model using its constructor.
But sometimes, I don't actually need an instance from that class, I just want to call some static functions from it. Also, there is a big limitation with $this->load('class_name'), it does not allow me to pass parameters to the constructor (unless we extend or modify the core class of CI).
I think the $this->load('class_name') function should only do a require_once on the class php file for me, and let me freely do things (create instance/call static functions) with the class in the controller.
Should I simply ignore this function and use require_once or writing my own __autoload function to load up the classes? This way, I just feel strange because it seems I am not writing codes inside the CI box.
You can pass parameters to your constructor. See the "Passing Parameters When Initializing Your Class" section in the user guide.
I found CodeIgniter's object creation and loading to be very limiting. I want full control over my code, and little magic in the background. I have instead started using Doctrine's Class Loader. It's very lightweight and is essentially SPL autoloading (also a good alternative). You don't need the whole Doctrine shebang with ORM and all that stuff, just the ClassLoader. There's some configuration tinkering to get this right, but it works wonders.
With PHP 5.3 I now have namespaced classes in the Application directory. For instance I created a new class in the Tests directory: Application\Tests\SomeTest.php
That test could look something like this:
namespace Tests;
class SomeTest {
...
}
I would use this class in my code (controllers, views, helpers) by simply using the fully qualified namespace (i.e. $test = new \Tests\SomeTest) or a "use" statement at the top of my code (use \Tests\SomeTest as SomeTest).
In this way I intend to replace all libraries and models with OO namespaced variants. There are many benefits to this: fast autoloading with SPL, full IDE intellisense support for classes/methods (CodeIgniter is really bad for that), your code is more portable to other frameworks or projects.
That said, I still use a lot of the CodeIgniter engine. This basically means I have $CI =& get_instance() in most of my classes. It's still a work in progress and I think the main reason I need CI is for it's database access. If I can factor that out ... and use something like Dependency Injection, then I won't need CodeIgniter in my classes at all. I will simply be using it for it's MVC framework, and using it's methods occasionally in my controllers.
I know this goes above and beyond your question, but hopefully it's some food for though - and it helps me to get it in writing too.