Every now and then I come across a problem with PHPs autoloading whereby class_exists fails to autoload classes. I’ve noticed this with a number of PHP versions, most recently with 5.3.2-1ubuntu4.9. Typically I’ve resolved this by simply upgrading the PHP version.

In the following example the initial class_exists fails until you instantiate the object and from that point the class exists.

PHP 5.3.2-1ubuntu4.9 with Suhosin-Patch (cli) (built: May 3 2011 00:43:34)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies
with Xdebug v2.1.0, Copyright (c) 2002-2010, by Derick Rethans

This example is simply using Zend Framework + Doctrines Annotations.

var_dump(class_exists('\Everlution\Annotations\Acl', true)); // bool(false)
$obj = new \Everlution\Annotations\Acl(array());
var_dump($obj);
var_dump(class_exists('\Everlution\Annotations\Acl', true)); // bool(true)

bool(false)
object(Everlution\Annotations\Acl)#160 (1) {
  ["_values":protected]=>
  array(0) {
  }
}
bool(true)