Description:
------------
PHP is generating a fatal error when a class that inherit from another is getting instantiated and these classes are defined after being instantiated. 

If the class does not inherit PHP run the code without errors.



Test script:
---------------
<?php

$a = new Aa();
$a->hi();


class Aa extends Bb
{

}

class Bb
{
    public function hi()
    {
        echo('hi Aa');
    }
}



Expected result:
----------------
hi Aa

Actual result:
--------------
PHP Fatal error:  Class 'Aa' not found in /home/www/test.php on line 3