PHP correctly decodes escape encoded characters in javascript

This is a collection of a long time ago, I don't know who wrote it, but after testing no problem ~
JavaScript code

 
function phpUnescape($escstr) 
{ 
preg_match_all("/%u[0-9A-Za-z]{4}|%.{2}|[0-9a-zA-Z.+-_]+/", $escstr, $matches); 
$ar = &$matches[0]; 
$c = ""; 
foreach($ar as $val) 
{ 
if (substr($val, 0, 1) != "%") 
{ 
$c .= $val; 
} elseif (substr($val, 1, 1) != "u") 
{ 
$x = hexdec(substr($val, 1, 2)); 
$c .= chr($x); 
} 
else 
{ 
$val = intval(substr($val, 2), 16); 
if ($val < 0x7F) // 0000-007F 
{ 
$c .= chr($val); 
} elseif ($val < 0x800) // 0080-0800 
{ 
$c .= chr(0xC0 | ($val / 64)); 
$c .= chr(0x80 | ($val % 64)); 
} 
else // 0800-FFFF 
{ 
$c .= chr(0xE0 | (($val / 64) / 64)); 
$c .= chr(0x80 | (($val / 64) % 64)); 
$c .= chr(0x80 | ($val % 64)); 
} 
} 
} 
return $c; 
} 

After the escape code:

 
%u6D4B%u8BD5www.jb51.net%22%22%27%27%3C%3E%26%26 

After the decoding:

 
 test www.jb51.net""''<>&&