ZF-2923: Zend_Loader::autoload() causes a file not found warning when unable to include the class
Autoload functions should not cause errors when they can't include the requested class. They may only be one function in the autoload stack, or they may be being used by class_exists() to simply check if a class is available. It isn't the job of any individual autoload to ensure a class is defined, therefore they should fail silently in the event that they cannot include the class.
At present the Zend_Loader::loadClass() method (used by Zend_Loader::autoload()) causes a PHP file not found warning if it cannot include the requested class. (Line 83)