What are the best practices for extending a library in PHP?
I'm using the bshaffer OAuth2 library. In my code, I instantiate the library like this:
//// Start up the OAuth2 server
require_once('./oauth2-server-php/src/OAuth2/Autoloader.php');
OAuth2\Autoloader::register();
All of the OAuth2 classes are under the namespace starting like OAuth2\foo\bar. I am able to extend these classes without specifying a namespace for my own classes by giving them a unique name (which I prefer not to do). However, I would like to create my own namespace in order to keep the actual class names the same when extending them.
For instance, when I try to extend the Pdo class this way, it says 'class Pdo already instantiated'.
class Pdo extends OAuth2\Pdo {
}
So I tried it this way. In MyServer.php, I have:
<?php
namespace MyNS;
class Server extends OAuth2\Server {
}
?>
But then I get an error that the class MyNS\OAuth2\Server does not exist. Obviously, it doesn't, and I don't think you can go 'up' a level with namespaces like you can with directories.
I've spent a fair amount of time reading the docs for PHP classes. I can extend the classes by renaming them (eg MyServer or MyPdo), but this seems messy and I feel like I should use my own name space. Or even MyNS\OAuth2 could work if I knew how to do it that way. Maybe I have to create my own autoloader for the classes (which I don't know how to do yet)?
Can someone please shine a light in my brain?
You were almost there with your own namespace - you just need an extra backslash \ to ensure that you are referring to the OAuth2 that is sitting in the global space. - i.e.
<?php
namespace MyNS;
class Server extends \OAuth2\Server {
// ^______________________ here
}
Related
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.
On a web project there are two classes that have the same name. This was never an issue until now, because the two classes where never used at the same time / in the same script.
Now we require to use both classes in one script, and therefor got ourselves an "Cannot redeclare class" fatal error.
My question is: What options are there to resolve this issue?
The one possible solution would be to rename one of the classes in question, but it is something I would very much like to avoid - one of the classes is part of a third-party software that should not be modified at this level, to remain updateable.
I know there are namespaces - are they a valid option to this problem? I have never used namespaces until now.
Assuming we would put one of the classes into a namespace: Would this resolve the issue? Also, what measures would we need to take to access the now-namespaced class?
Namespaces would surely solve your problem.
For example I got multiple classes named 'core', but because they're all classes of a different namespace it doesn't give any conflict at all.
This does mean you have to go over all your code and refer to the namespaced class with the correct path.
$item = new doubleClass();
would become
$item = new \my_namespace\doubleClass();
Also make sure that your other scripts don't get namespaced otherwise it wouldn't be able to find the non namespaced class anymore.
How Namespace work:
consider we have 2 classes named User in file structure
/Package1/User.php
with content
<?php
namespace Package1;
class user {...}
and
/Package2/User.php
with content
<?php
namespace Package2;
class user {...}
and now for some reason we decide to use both in some class UserManager in:
/Package3/UserManager.php
with content:
<?php
namespace /Package3;
use package1/User as User1;
use package2/User as User2;
class UserManager {
public function __construct(User1 $user1, User2 $user2) {...}
...
}
I have a file with a class Resp. The path is:
C:\xampp\htdocs\One\Classes\Resp.php
And I have an index.php file in this directory:
C:\xampp\htdocs\Two\Http\index.php
In this index.php file I want to instantiate a class Resp.
$a = new Resp();
I know I can use require or include keywords to include the file with a class:
require("One\Classes\Resp.php"); // I've set the include_path correctly already ";C:\xampp\htdocs". It works.
$a = new Resp();
But I want to import classes without using require or include. I'm trying to understand how use keyword works. I tried theses steps but nothing works:
use One\Classes\Resp;
use xampp\htdocs\One\Classes\Resp;
use htdocs\One\Classes\Resp;
use One\Classes;
use htdocs\One\Classes; /* nothing works */
$a = new Resp();
It says:
Fatal error: Class 'One\Classes\Resp' not found in C:\xampp\htdocs\Two\Http\index.php
How does the keyword use work? Can I use it to import classes?
No, you can not import a class with the use keyword. You have to use include/require statement. Even if you use a PHP auto loader, still autoloader will have to use either include or require internally.
The Purpose of use keyword:
Consider a case where you have two classes with the same name; you'll find it strange, but when you are working with a big MVC structure, it happens. So if you have two classes with the same name, put them in different namespaces. Now consider when your auto loader is loading both classes (does by require), and you are about to use object of class. In this case, the compiler will get confused which class object to load among two. To help the compiler make a decision, you can use the use statement so that it can make a decision which one is going to be used on.
Nowadays major frameworks do use include or require via composer and psr
1) composer
2) PSR-4 autoloader
Going through them may help you further.
You can also use an alias to address an exact class. Suppose you've got two classes with the same name, say Mailer with two different namespaces:
namespace SMTP;
class Mailer{}
and
namespace Mailgun;
class Mailer{}
And if you want to use both Mailer classes at the same time then you can use an alias.
use SMTP\Mailer as SMTPMailer;
use Mailgun\Mailer as MailgunMailer;
Later in your code if you want to access those class objects then you can do the following:
$smtp_mailer = new SMTPMailer;
$mailgun_mailer = new MailgunMailer;
It will reference the original class.
Some may get confused that then of there are not Similar class names then there is no use of use keyword. Well, you can use __autoload($class) function which will be called automatically when use statement gets executed with the class to be used as an argument and this can help you to load the class at run-time on the fly as and when needed.
Refer this answer to know more about class autoloader.
use doesn't include anything. It just imports the specified namespace (or class) to the current scope
If you want the classes to be autoloaded - read about autoloading
Don’t overthink what a Namespace is.
Namespace is basically just a Class prefix (like directory in Operating System) to ensure the Class path uniqueness.
Also just to make things clear, the use statement is not doing anything only aliasing your Namespaces so you can use shortcuts or include Classes with the same name but different Namespace in the same file.
E.g:
// You can do this at the top of your Class
use Symfony\Component\Debug\Debug;
if ($_SERVER['APP_DEBUG']) {
// So you can utilize the Debug class it in an elegant way
Debug::enable();
// Instead of this ugly one
// \Symfony\Component\Debug\Debug::enable();
}
If you want to know how PHP Namespaces and autoloading (the old way as well as the new way with Composer) works, you can read the blog post I just wrote on this topic: https://enterprise-level-php.com/2017/12/25/the-magic-behind-autoloading-php-files-using-composer.html
You'll have to include/require the class anyway, otherwise PHP won't know about the namespace.
You don't necessary have to do it in the same file though. You can do it in a bootstrap file for example. (or use an autoloader, but that's not the topic actually)
The issue is most likely you will need to use an auto loader that will take the name of the class (break by '\' in this case) and map it to a directory structure.
You can check out this article on the autoloading functionality of PHP. There are many implementations of this type of functionality in frameworks already.
I've actually implemented one before. Here's a link.
I agree with Green, Symfony needs namespace, so why not use them ?
This is how an example controller class starts:
namespace Acme\DemoBundle\Controller;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
class WelcomeController extends Controller { ... }
Can I use it to import classes?
You can't do it like that besides the examples above. You can also use the keyword use inside classes to import traits, like this:
trait Stuff {
private $baz = 'baz';
public function bar() {
return $this->baz;
}
}
class Cls {
use Stuff; // import traits like this
}
$foo = new Cls;
echo $foo->bar(); // spits out 'baz'
The use keyword is for aliasing in PHP and it does not import the classes. This really helps
1) When you have classes with same name in different namespaces
2) Avoid using really long class name over and over again.
Using the keyword "use" is for shortening namespace literals. You can use both with aliasing and without it. Without aliasing you must use last part of full namespace.
<?php
use foo\bar\lastPart;
$obj=new lastPart\AnyClass(); //If there's not the line above, a fatal error will be encountered.
?>
Namespace is use to define the path to a specific file containing a class e.g.
namespace album/className;
class className{
//enter class properties and methods here
}
You can then include this specific class into another php file by using the keyword "use" like this:
use album/className;
class album extends classname {
//enter class properties and methods
}
NOTE: Do not use the path to the file containing the class to be implements, extends of use to instantiate an object but only use the namespace.
I have studied the use of Namespaces in PHP a while back but recently looking at a project that used the use keyword and then accessed the namespaced object as if they were normal without namespace.
My question is, is the code below correct, it hs a file index.php and uses the namespace MyLibrary\Base it then uses use to bring in \MyLibrary\Registry \MyLibrary\User and \MyLibrary\Request
It then can access any of these object without putting there namespace in front of them, so the actual code below the use section looks like a normal pre-namespace php file.
I am asking if this is how you use namespaces? Or am I missing something?
File: index.php
<?php
namespace MyLibrary\Base;
use \MyLibrary\Registry;
use \MyLibrary\User;
use \MyLibrary\Request;
class Base
{
public $registry;
function __construct($registry)
{
$this->registry = $registry;
$this->user = New User;
$this->request = new Request;
# code...
}
}
?>
File: registry.class.php
<?php
namespace MyLibrary\Registry;
class Registry
{
public $user;
function __construct($user)
{
$this->user = $user;
# code...
}
}
?>
Yes. The use-statement imports the class- or namespace-name into the current scope. To write everything that short is the reason, why the PHP-devs implemented namespaces ;)
namespace MyFirstNamespace {
class Foo {}
}
namespace MySecondNamespace {
use \MyFirstNamespace\Foo as Bar;
$foo = new Bar;
}
a) it make everything more readable, because its much shorter, than Vendor_Package_Foo_Bar_XyzClass and b) you can exchange the classes to use very fast.
# use \MyFirstNamespace\Foo as Bar; // I don't like Foo anymore
use \MyFirstNamespace\SimilarToFoo as Bar;
Namespacing has a lot of advantages to it.
The first on is you can reuse method names and even class names if it makes sense provided they exist within a different namespace. Example:
namespace \myNamespace\data\postgres;
class DataBase extends \PDO
{
}
namespace \myNamespace\data\mysql;
class DataBase extends \PDO
{
}
You could even reuse names that are normally reserved for PHP functions
namespace \myNamespace\dir;
function makedir ()
{
if (// some condition is true)
{
\makedir ();
}
}
All of this is intended to make it easier to use code from different sources together without having to worry about naming conflicts. Provided programmers are courteous enough to observe a few simple rules then the chances of name conflicts are hugely reduced. Actually, pretty much the only rule you need to concern yourself with to avoid naming conflicts is to make the first level of your namespace your own. For example, use your company name, or some other way of identifying you as a unique vendor as the first level of your namespace and everything should be good.
For example I use \gordian as the root namespace in all the code I write, as I can then call my classes under that namespace anything I like without worrying about them colliding with someone who chose a different root namespace.
So what's wrong with PEAR conventions, you might ask? A lot of projects follow them, including the popular Zend framework.
The answer is names become very unwieldy very quickly. For instance, Zend, as it follows the PEAR convention, uses a sort of pseudo-namespacing. All the classes in the collection start with Zend_ and with each level of class hierachy add a further part to the name.
Ze
As a result, you end up with class names like Zend_Db_Adaptor_Abstract and Zend_Dojo_Form_Decorator_TabContainer.
Should Zend update their framework to use namespaces (which I'm told is happening with Zend Framework 2.0) then they'd be replaced with \Zend\Db\Adaptor\Abstract and \Zend\Dojo\Form\Decorator\TabContainer instead. So what, you might ask? The answer is that you can alias them to much shorter names with the Use keyword, as you've already seen. This means you don't have to keep writing the full class name out, but only as far as to what you've aliased.
use \Zend\Dojo\Forn\Decorator as Dec;
$a = new Dec\TabContainer; // Not easy to do without namespaces!
Further more, if you're already in a given namespace, then you don't even have to use the use keyword to access other items within the same namespace by a short name, as it happens automatically for you in that case. For framework writers this is a huge timesaver.
For example, you might see something like the followign in Zend Framework 2 (as I'm not working on it in any way, this is purely an example and not from the actual ZF2 source).
namespace \Zend\Db\Adaptor;
class Postgres extends Abstract // We don't need to use \Zend\Db\Adaptor\Abstract here because it's in the same namespace already anyway
{
}
There are other benefits too, such as it makes autoloaders ridiculously simple to make (provided your namespace structure maps exactly onto your filesystem directory structure).
Namespaces can seem like one of those features that aren't really very important, or don't even seem to make any sense, but after using them for a little while their usefulness will suddenly become very obvious.
Recently I have started to play around with Namespaces in PHP, I am not a fan of the chosen Namespace separator / (as most others have a mutual feeling) /
Below I have a very basic/simple example of using Namespace in PHP.
I have a Registry.class.php file that has a Registry class that is in the Namespace Library
I also have the file Controller.class.php below that has a Controller class that is in the Namespace called Project
Now in this Project Namespace I need access to the Registry object that is in a different Namespace, Library So I use use Library\Registry to Import that Namespace
With that done, I am able to simply access my Registry class like this...
$this->registry = new Registry;
Now if I had not used use Library\Registry then I would have to access it like this
$this->registry = new /Library/Registry;
So this is where my question begins.
For this simple example I am just bringing in the Registry class, in a real project, imagine several other classes and namespaces being brought in, So I would be using
use Library\Registry and use Library\SOME OTHER CLASS and use Library\YET ANOTHER CLASS etc...
I can then operate on the Objects/classes as if they were in this namespace to begin with so instead of pre-fixing the class name with its appropriate Namespace name, I simply just instantiate the class by its name ( new Registry;) instead of new /Library/Registry;
I would like to know if this is considered bad practice or not? It greatly simplify's things and makes the code look cleaner IMO, but if there is anything bad about this method I would like to know before I write a lot of code using this method. Should I be pre-fixing my classes when I instantiate them with their namespace INSTEAD of importing them with the use /Path/to/Namespace/Classname ?
Please share your knowledge with me, I realize it will work either way but I want to make sure. Example classes and namespaces are added below:
Controller.class.php
<?php
namespace Project
{
use Library\Registry;
class Controller
{
public $registry;
function __construct()
{
include('E:\Library\Registry.class.php');
$this->registry = new Registry;
}
function show()
{
$this->registry;
echo '<br>Registry was ran inside testcontroller.php<br>';
}
}
}
?>
Registry.class.php
<?php
// Registry.class.php
namespace Library
{
class Registry
{
function __construct()
{
echo 'Registry.class.php Constructor was ran';
}
}
}
?>
One of the primary purposes of namespaces is to prevent name conflicts in large code bases and across shared code and imported libraries. If you're not having name conflict issues, then I don't necessarily see anything wrong with using each class. If you find yourself doing this for all your classes, however, then I would question why you're using namespaces in the first place. This would only seem to make sense to me if your code was going to be used as an API or library by someone else.