php通过字符串生存hashCode

/**
 * 
 * 生存hashCode
 *
 */
function hashCode($str){
    if(empty($str))
        return '';
    $str = strtoupper($str);
    $mdv = md5($str);
    $mdv1 = substr($mdv,0,16);
    $mdv2 = substr($mdv,16,16);
    $crc1 = abs(crc32($mdv1));
    $crc2 = abs(crc32($mdv2));
    return bcmul($crc1,$crc2);
}