Php实现Js的escape方法

//php function
   
function escape($string) {
                $n = $bn = $tn = 0;
                $output = '';
                $special = "-_.+@/*0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
                while($n < strlen($string)) {
                        $ascii = ord($string[$n]);
                        if($ascii == 9 || $ascii == 10 || (32 <= $ascii && $ascii <= 126)) {
                                $tn = 1;$n++;
                        } elseif(194 <= $ascii && $ascii <= 223) {
                                $tn = 2;$n += 2;
                        } elseif(224 <= $ascii && $ascii <= 239) {
                                $tn = 3;$n += 3;
                        } elseif(240 <= $ascii && $ascii <= 247) {
                                $tn = 4;$n += 4;
                        } elseif(248 <= $ascii && $ascii <= 251) {
                                $tn = 5;$n += 5;
                        } elseif($ascii == 252 || $ascii == 253) {
                                $tn = 6;$n += 6;
                        } else {
                                $n++;
                        }
                        $singleStr = substr($string,$bn,$tn);
                        $charVal = bin2hex(iconv('utf-8', 'ucs-2', $singleStr));
                        if(base_convert($charVal, 16, 10) > 0xff) {
                             if (!preg_match("/win/i", PHP_OS))
                                $charVal = substr($charVal, 2, 2).substr($charVal, 0, 2);                            
                            $output .= '%u' . $charVal;
                        } 
                        else {
                                if(false !== strpos($special, $singleStr))
                                     $output .= $singleStr;                               
                                else 
                                     $output .="%" . dechex(ord($string[$bn]));
                        }

                  $bn = $n;
                }
return $output;
}