PHP计算哈希HASH

<?php                                      
header("Content-type: text/html; charset=utf-8");
include_once '/var/www/html/api/com/com_inc.php';

class HashUtil {
	const s_M = 251;
       
    public static function cal($_data, $len) {
		Log::info("HashUtil::cal", Log::INFO);
		try {
            $_data = FuncUtil::chrToByts($_data, 0, $len);
           
            $_h = 0;
            $_a = 31415;
            $_b = 27183;
            
		    for ($i = 0; $i < $len; $i++) {
                $_val = $_data[$i];
                //echo $_val . " ";
                if ($_val >= 128) {
                    $_val = $_val - 256;
                } 
                $_h = ($_a * $_h + $_val) % self::s_M;
		        $_a = $_a * $_b % (self::s_M-1);
		    }
            
            return ($_h < 0) ? ($_h + self::s_M):$_h;
		} catch (Exception $e) {
			Log::info("UTCToChr Exception: " . $e->getMessage(), Log::EXCEPT);
		}
    }
}
?>