I stated implementing object oriented design into my website. I'm using php, and ran into an issue.
As is my tendency, I like to define one class per one file - nothing else. Normally, if I remember correctly, in most languages classes can be called if they're in the same directory without having to be explicitly linked to the main program (I could be wrong, or unique to virtual machines).
Right now, php sends errors when I don't link the class file to the main file. On top of that, a child class won't execute unless I define the link to the parent's class file.
Do I have to explicitly link all of my files together?
Here's some snippets of my code for detail:
<?php
include_once 'VRC_Header2.php';
include_once 'UserService.php'; //Child class file of DB_MySQL.php
include_once 'DB_MySQL.php'; //Parent class
//Without the two links above, this file will not execute
Then the child class:
class UserService extends DB_MySQL
{...
Any help is appreciated.
Yes, in PHP, you have to include all classes you need before you instanciate them.
One method to circumvent this is to use autoloading:
http://php.net/manual/en/language.oop5.autoload.php
Which is used on most PHP Frameworks (e.g. Zend Framework).
You have to include all class files to one another. Otherwise other pages will not understand where the class is present.
You can use namespace concept.
http://php.net/manual/en/language.namespaces.php
But in this you have to include the class files.
Related
This is what I have at hand:
//Person.php
namespace Entity;
class Person{
}
User file:
//User.php
use Entity\Person;
$person = new Person;
Here, it fails if I don't include the Person.php file. If I include it, the everything works fine. Do I absolutely require to include the file even when using namespaces? If at all we need to include/require files, then how can namespaces be effectively used? Also, can we maintain folder structure by nesting namespaces?
The answer to your question is "yes and no".
Indeed the code implementing class Person has to be included, otherwise the class is not defined and cannot be used. Where should the definition come from, when the code is not included? The php interpreter cannot guess the classes implementation. That is the same in all programming languages, by the way.
However there is something called Autoloading in php. It allows to automatically include certain files. The mechanism is based on a mapping of class names to file names. So in the end it boils down to php searching through a folder structure to find a file whos name suggests that it implements a class currently required in the code it executes.
But don't get this wrong: that still means the file has to be included. The only difference is: the including is done automatically, so without you specifying an explicit include or require statement.
Yes, you need to include every file.
A very good example can be found here on effective usage of namespaces.
With PSR-0 autoloading, the namespace has to be the same as the folder in which the class is, file the filename has to be the same as the classname. This gives you very simple and effective autoloading with composer for example.
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.
I am using Vzaar's PHP Library for uploading videos from my website to their server space.
Now point is - in their library there are some PHP files in which more than one class exists and no class with same file name exists in same file.
i.e. have a look at OAuth.php, there is no class with name OAuth in that file.
Question raised in my mind is
When I create any PHP class file, can I create multiple classes in side one file, and later I can use that file in my code or I can use that reusable code in other project as well.
Should creating such files is good practice?
If the class is of 15 to 20 lines long, then should I create a separate file or I should include that in one file only, like OAuth.php.
Please guide with exact reason, if I will get links of wiki where proper explanation is given, then it will be best.
Putting more than one class in one file in general is a bad practice, and in Symfony2 even more because of the way class autoloader works.
When autoloader is looking for Acme\DemoBundle\SomeClass class it expects it will be in Acme\DemoBundle\SomeClass.php file. So in case you have a second class in the same file it won't work.
Check also PSR standards for class autoloading.
Despite I don't like to define more than one class per file I would like to point it out that PSR-4 is not against this practice if the class scope is private.
Quoting Symfony2 coding standards resource (http://symfony.com/doc/current/contributing/code/standards.html)
Define one class per file - this does not apply to private helper
classes that are not intended to be instantiated from the outside and
thus are not concerned by the PSR-0 and PSR-4 autoload standards;
In this other example (Thanks to Xavi Montero) you can see that the class Psr4AutoloaderClassTest has a helper class MockPsr4AutoloaderClass defined in the same file. So in general you should not, but for a "private helper" it's okey.
https://www.php-fig.org/psr/psr-4/examples
This is what I have at hand:
//Person.php
namespace Entity;
class Person{
}
User file:
//User.php
use Entity\Person;
$person = new Person;
Here, it fails if I don't include the Person.php file. If I include it, the everything works fine. Do I absolutely require to include the file even when using namespaces? If at all we need to include/require files, then how can namespaces be effectively used? Also, can we maintain folder structure by nesting namespaces?
The answer to your question is "yes and no".
Indeed the code implementing class Person has to be included, otherwise the class is not defined and cannot be used. Where should the definition come from, when the code is not included? The php interpreter cannot guess the classes implementation. That is the same in all programming languages, by the way.
However there is something called Autoloading in php. It allows to automatically include certain files. The mechanism is based on a mapping of class names to file names. So in the end it boils down to php searching through a folder structure to find a file whos name suggests that it implements a class currently required in the code it executes.
But don't get this wrong: that still means the file has to be included. The only difference is: the including is done automatically, so without you specifying an explicit include or require statement.
Yes, you need to include every file.
A very good example can be found here on effective usage of namespaces.
With PSR-0 autoloading, the namespace has to be the same as the folder in which the class is, file the filename has to be the same as the classname. This gives you very simple and effective autoloading with composer for example.
I need to find a way to skip require_once error in case 2 php classes, with same name, are called in a file.
I have 2 files a.php and b.php and each of them have class A declared inside.
Inside index.php I first include a.php file which has class A declared. Also inside index.php I must include c.php, which inside it has require_once b.php and for this reason I get duplicate classname error and the script is stopped.
Can I find a workaround for this?
Thanks for your reply
Let me explain it better.
Is about Joomla and I build a plugin to overwrite a component models and views. I included my models and views classes in the plugin and Joomla uses them instead of the original component models and views classes.
The problem appears when a component module is including the component original models and views classes with require_once.
Since my plugin is not using the original models classes, so the file where the original models classes are, is not included inside Joomla, the module require_one is able to include the component model classes, and those classes has the same name as my plugin ones.
I can only change my plugin code and classes and not component classes, the second ones.
I need to find a way to skip require_once error in case 2 php classes, with same name, are called in a file.
No you don't. You shouldn't have 2 classes in the same file. Uhhhmm lemme rephrase that. You cannot have two classes with the same name (unless namespaced). But seriously you shouldn't have two classes in 1 file.
I have 2 files a.php and b.php and each of them have class A declared inside.
I guess (/ hope) they are not the same classes because that would violate (rape) the DRY principle.
Can I find a workaround for this?
Don't copy the same class. If both classes are different namespace it. Either the new way with real namespaces or the old way:
namespace Lib\Your\Namespace;
or
class Lib_Your_Namespace
wrap the require call in
if(!class_exists('your_class_name')) {
require_once('file_name');
}
I think that the namespace - this is what you need