How do I implement the escape and unescape functions of javascript using PHP

Front-end developers know that javascript has the encoding function escape() and the corresponding decoding function unescape(), while there are only urlencode and urldecode in php. This encoding and decoding function is valid for encodeURI and encodeURIComponent, but not for escape.
escape() function and unescape() function user string encoding in javascript, similar to urlencode() function in PHP, here is the escape function code implemented by php:

/** 
 * js escape php  implementation  
 * @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) { //  Multibyte character  
                $return .= '%u' . strtoupper ( bin2hex ( mb_convert_encoding ( $str, $out_encoding, $in_encoding ) ) ); 
            } else { 
                $return .= '%' . strtoupper ( bin2hex ( $str ) ); 
            } 
        } 
    } 
    return $return; 
}

The corresponding decoded php unescape code is:

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; 
}