php create class method at runtime

Question

I am wondering if there is a way to attach a new method to a class at runtime, in php. I mean, not on an instance level but directly to the class, so that all newly created instances, have this new method. Can such a thing be done with reflection?

Thanks

Answer 1

Yes, you can.

Below is the way to create method in runtime in php 5.4.x.

The anonymous function is represented by Closure class started from 5.3.x. From 5.4.x, it add a Closure::bind static method to bind the anonymous function to a particular object or class.

Example:

class Foo {
     private $methods = array();

     public function addBar() {
       $barFunc = function () {
         var_dump($this->methods);
       };
       $this->methods['bar'] = \Closure::bind($barFunc, $this, get_class());
     }

     function __call($method, $args) {
          if(is_callable($this->methods[$method]))
          {
            return call_user_func_array($this->methods[$method], $args);
          }
     }
 }

 $foo = new Foo;
 $foo->addBar();
 $foo->bar();

Answer 2

Did some playing around with whole thing. Seems that only thing you can potentially do with ReflectionClass is to replace an existing method. But even that would be indirectly.

I actually do not know any class-based language, where dynamic classes exist (then again, my knowledge is quite limited). I have seen it done only in prototype-based languages (javascript, ruby, smalltalk). Instead what you can do, in PHP 5.4, is to use Closure and add new methods to an existing object.

Here is a class which would let you perform such perversion to any object:

class Container
{
    protected $target;
    protected $className;
    protected $methods = [];

    public function __construct( $target )
    {
        $this->target = $target;
    }

    public function attach( $name, $method )
    {
        if ( !$this->className )
        {
            $this->className = get_class( $this->target );
        }
        $binded = Closure::bind( $method, $this->target, $this->className );
        $this->methods[$name] = $binded;
    }

    public function __call( $name, $arguments )
    {
        if ( array_key_exists( $name, $this->methods ) )
        {
            return call_user_func_array( $this->methods[$name] , $arguments );
        }

        if ( method_exists( $this->target, $name ) )
        {
            return call_user_func_array( 
                array( $this->target, $name ),
                $arguments
                );
        }
    }   
}

To use this, you have to provide constructor with an existing object. Here is small example of usage:

class Foo
{
    private $bar = 'payload';
};
$foobar = new Foo;
// you initial object


$instance = new Container( $foobar );
$func = function ( $param )
{
    return 'Get ' . $this->bar . ' and ' . $param;
};
$instance->attach('test', $func);
// setting up the whole thing


echo $instance->test('lorem ipsum');
// 'Get payload and lorem ipsum'

Not exactly what you want, but AFAIK this is as close you can get.

Answer 3

Have you taken a look at create_function() in the docs? You might also achieve the desired result by overloading.

Answer 4

This is possible with the runkit extension's runkit_method_add(). Be careful using this in production though.

Example:

<?php
class Example {}

$e = new Example();

runkit_method_add(
    'Example',
    'add',
    '$num1, $num2',
    'return $num1 + $num2;',
    RUNKIT_ACC_PUBLIC
);

echo $e->add(12, 4);

Answer 5

You can use one of the below two methods also.

function method1()
{
    echo "In method one.";
}

function method2()
{
    echo "In method two.";
}

class DynamicClass
{
    function __construct(){
        $function_names = ['method1'];
        foreach ($function_names as $function_name) {
            if (function_exists($function_name)) {
                $this->addMethod($function_name);
            }
        }
    }

    function addMethod($name)
    {
        $this->{$name} = Closure::fromCallable($name);
    }

    public function __call($name, $arguments)
    {
        return call_user_func($this->{$name}, $arguments);
    }
}


$obj = new DynamicClass();
//Call method1 added in constructor
$obj->method1();
//Add method
$obj->addMethod('method2');
$obj->method2();