Mine

 public string GetTag(string value)
 {
    UInt32 hex = Convert.ToUInt32("0x" + value, 16);
    return ((hex & 0x000000FFU) << 24 | (hex & 0x0000FF00U) << 8 |
                   (hex & 0x00FF0000U) >> 8 | (hex & 0xFF000000U) >> 24).ToString();
 }


function GetTag($value){
        $hex = HexToInt($value);

        return (($hex & 0x000000FFU) << 24 | ($hex & 0x0000FF00U) << 8 |
                   ($hex & 0x00FF0000U) >> 8 | ($hex & 0xFF000000U) >> 24);
}