!class_exists is not working in magento? - php

Question

When I run test.php, why always error on !class_exists line?
This is test.php:
<?php //test.php
require_once './app/Mage.php';
Mage::app()->setCurrentStore(0);
Mage::setIsDeveloperMode(true);
require_once("test-class.php");
?>
This is test-class.php:
<?php //test-class.php
if (!class_exists("AClass")) {
class AClass {
public function AnAction() {
return 123;
}
}
}
?>

Answer 1

Because the Magento bootstrap app/Mage.php registers an autoloader, your call to class_exists() triggers attempts to load a class definition for this class. This behavior can be changed by passing false:
<?php //test-class.php
if (!class_exists("AClass",false)) {
class AClass {
public function AnAction() {
return 123;
}
}
}
?>
Further, the bootstrap sets up include path arguments for use by the autoloader:
$paths[] = BP . DS . 'app' . DS . 'code' . DS . 'local';
$paths[] = BP . DS . 'app' . DS . 'code' . DS . 'community';
$paths[] = BP . DS . 'app' . DS . 'code' . DS . 'core';
$paths[] = BP . DS . 'lib';
Placing your class definition in any of the above directories will allow it to be defined whenever a definition is required.