HackerPro536 Function Decode PHP obfuscated

<?php /* HackerPro536 Function Decode PHP vanphu113 */
if(!function_exists("hackerpro536"))
{ function hackerpro536($vanphu113) {
    $hvngroups="";
    $hvn=0;
    $hvngroups_net=strlen($vanphu113);
    while($hvn < $hvngroups_net) {
        if($vanphu113[$hvn] == ' ') {
            $hvngroups.=" "; }
        else if($vanphu113[$hvn] == '!') {
            $hvngroups.=chr((ord($vanphu113[$hvn+1])-ord('A'))*16+(ord($vanphu113[$hvn+2])-ord('a')));
            $hvn+=2;}
        else { $hvngroups.=chr(ord($vanphu113[$hvn])+1); }
        $hvn++;
        }
    return $hvngroups;
    }
}
echo(hackerpro536('Code paste here')); ?>
Read More: http://hvngroups.net/hvn/huong-dan-decode-php-obfuscated-2535.hvn