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Update: there’s a serious bug with this approach and `runkit` 0.7. For an updated approach, try Revisiting multiple inheritance in PHP. Oh, there are RPM packages for runkit here.

Here’s some code that will help you simulate multiple inheritance in PHP 5 with maximum portability. This requires the runkit extension for PHP, regrettably. Hope runkit gets rolled into baseline PHP 5.

This code also emulates the aggregate_methods function from the Object aggregation functions in PHP 4.

Say you have:

<?php
class Foo {
   function example() {
       return "foo!\n";
   }
}

class Bar { // initially, no methods }

// copy the example() method from the Foo class to the Bar class, as baz() runkit_method_copy('Bar', 'baz', 'Foo', 'example');

// output copied function echo Bar::baz(); ?>

We can generalize the runkit_method_copy to work with all classes:

<?php

function aggregate_methods($destClassName,$srcClassName) { $methods = get_class_methods($srcClassName); foreach ($methods as $m) { runkit_method_copy($destClassName,$m,$srcClassName,$m); } }

function inherits_from($destClassName,$srcClassNameList) { foreach ($srcClassNameList as $s) { aggregate_methods($destClassName,$s); } }

?>

Now, the function call will work for all classes without modification (honorable exception made of classes whose method namespaces clash). This little bit of magic lets you ‘inherit’ from multiple classes, taking full advantage of methods defined in other classes (such as classes written explicitly to work as mix-ins). Most of the introspection machinery won’t exactly work, but those are the breaks.

In practical terms:

<?php

class A { ...A' methods here... }

class B { ...B' methods here... }

class C { ...C's methods here... }

class MultipleInheritedClass { ...this class' methods here... } inherits_from('MultipleInheritedClass',array('A','B','C'));

?>

So there you go: there is multiple inheritance available in PHP!

This entry was posted on Tuesday, March 14th, 2006 at 17:47 and is filed under PHP, Programming, Software bacán. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.