php 模拟 javascript escape unescape函数

function unescape($str)
{
$ret = '';
$len = strlen($str);
for ($i = 0; $i < $len; $i ++)
{
if ($str[$i] == '%' && $str[$i + 1] == 'u')
{
$val = hexdec(substr($str, $i + 2, 4));
if ($val < 0x7f)
$ret .= chr($val);
else
if ($val < 0x800)
$ret .= chr(0xc0 | ($val >> 6)) .
chr(0x80 | ($val & 0x3f));
else
$ret .= chr(0xe0 | ($val >> 12)) .
chr(0x80 | (($val >> 6) & 0x3f)) .
chr(0x80 | ($val & 0x3f));
$i += 5;
} else
if ($str[$i] == '%')
{
$ret .= urldecode(substr($str, $i, 3));
$i += 2;
} else
$ret .= $str[$i];
}
return $ret;
}

/**
* js escape php 实现
* @param $string           the sting want to be escaped
* @param $in_encoding
* @param $out_encoding
*/
function escape($string, $in_encoding = 'UTF-8',$out_encoding = 'UCS-2') {
$return = '';
if (function_exists('mb_get_info')) {
for($x = 0; $x < mb_strlen ( $string, $in_encoding ); $x ++) {
$str = mb_substr ( $string, $x, 1, $in_encoding );
if (strlen ( $str ) > 1) { // 多字节字符
$return .= '%u' . strtoupper ( bin2hex ( mb_convert_encoding ( $str, $out_encoding, $in_encoding ) ) );
} else {
$return .= '%' . strtoupper ( bin2hex ( $str ) );
}
}
}
return $return;
}