PHP and circular dependencies

2007-08-14 10:44 pm 3 Comments , and

Today I noticed the strangest bug in PHP. Apparently there's a problem with circular dependencies and interfaces.

This is how the problem occurs:

  1. <?php 
  2.  
  3.   // this is class1.php
  4.  
  5.   require_once 'iclass.php';
  6.  
  7.   class class1 implements iclass {
  8.  
  9.   }
  10.  
  11. ?>
  1. <?php
  2.  
  3.   // this is class2.php
  4.  
  5.   require_once 'class1.php';
  6.  
  7.   class class2 extends class1 {
  8.  
  9.   }
  10.  
  11. ?>
  1. <?php 
  2.  
  3.   // this is iclass.php
  4.  
  5.   require_once 'class2.php';
  6.  
  7.   interface iclass {
  8.  
  9.      function setSomething(class2 $object);
  10.  
  11.   }
  12.  
  13. ?>

Now, if you run class1.php, you will get the following error:

  1. Fatal error: Class 'class1' not found in /home/filemobile/testscript/class2.php on line 5

I know this is not proper OOP, but its still a strange error. Normally PHP is pretty good at these weird structures ;). Weirdest thing was that it happened for me on one server, but not the other.

There is a bug marked bogus for this, which is understandable. It would be great though if the PHP could somehow throw an error thats a bit more helpful =P. Its a strange error, especially since I could only reproduce it with this structure, and not with for example just 2 classes with circular dependencies.

 1

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My name is Evert, and I've been writing semi-regularly on this blog since 2006.

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