Description:
------------
runkit.internal_override is On in php.ini:

Several runs of reproduce code in first 1-4 times finished 
correctly, but then I see very strange errors like:
Fatal error: Cannot redeclare __autoload() (previously 
declared in /var/www/_SHARED_/autoload.php:114322992) in 
/var/www/_SHARED_/autoload.php on line 47
or
Fatal error: Cannot redeclare __autoload() (previously 
declared in /var/www/_SHARED_/autoload.php:17) in 
/var/www/_SHARED_/autoload.php on line 47


Reproduce code:
---------------
<?
var_dump(substr('&#1090;&#1077;&#1089;&#1090;', 0, 2));
var_dump(mb_substr('&#1090;&#1077;&#1089;&#1090;', 0, 2));
runkit_function_remove('substr');
runkit_function_rename('mb_substr', 'substr');
#runkit_function_redefine('substr','$a,$b,$c','return mb_substr($a,$b,$c);'); # as variant
var_dump(substr('&#1090;&#1077;&#1089;&#1090;', 0, 2));
?>