Question

I’m looking for a solution on how to use argument list for instantiating class’ dynamically.

For example:

class test {
    
    public function __call($name, $args){
        /* blah, blah class exists? require */
        return new $name($args);
    }

    public function __toString(){
        return (string) $this->extension(); // to enforce __toString of extension
    }
}

class extension extends test {
    public function __construct(classTypeHint $object, $required, $random = 25){
        // This does not work, results in:
        // "Argument 1 passed to extension::__construct must be an instance of classTypeHint, array given...
    }

    public function __toString(){
        return var_export($this, true);
    }
}

echo new test;

As comment states, that results in error, but I’m looking to be able to access $object as ($args[0]), $required as ($args[1]) etc. Plus, enforce "correct" arguments.

Why am I looking for this?

The __autoload functionality of PHP is limited. Well, maybe it’s not, but I have not found an easy way to differentiate class autoloads.

With this functionality, I can use __call(), __get(), __callStatic() for three different autoloads. Like:

1. __call() looks for libraries in /includes/libraries
2. __get() looks for plugins in /application/plugins
3. __callStatic() looks for, umm, cats in /application/cats

If there is a better way through autoloading, please share. But I’m still looking for such a solution, if it’s possible. Maybe with Reflection classes?

Somewhat working example with ReflectionClass:

$instance = new ReflectionClass($name);
$instance->newInstanceArgs($arguments);
return $instance;

But it’s obvious here, that it will call ReflectionClass->__toString() here. Plus, overlooking the returned dump, it actually does not use the newInstanceArgs() here.

Notes:

I’m interested in example working prior to PHP 5.3.

Answer 1

Use reflection:

public function __call($name, $args)
{
    return (new ReflectionClass($name))->newInstanceArgs($args);
}

it takes an array just like call_user_func_array

Edit: a working example: http://codepad.org/ZZpBwRij

<?php

class MyClass
{
    public function __construct($a, $b)
    {
        echo "__construct($a, $b) called";
    }
}

function create($name, $args)
{
    $class = new ReflectionClass($name);
    return $class->newInstanceArgs($args);
}

var_dump(create('MyClass', array(1, 2)));

?>

Output:

__construct(1, 2) called
object(MyClass)#2 (0) {
}