function for signing values

SecureHash.php

<?php

class SecureHash
{

    const SECRET = 'PUT_YOUR_SECRET_HERE';
    const SEPARATOR = '|';

    /**
     * hash string
     *
     * @param string $valueToSign value to sign
     * @param string $secretValue additional sign secret
     * @return string
     */
    private static function hashString($valueToSign, $secretValue = null)
    {
        return hash_hmac('sha1', $valueToSign, $secretValue . self::SECRET);
    }

    /**
     * generate signed value
     *
     * @param $valueToSign
     * @param string $secretValue additional sign secret
     * @return string
     */
    static function makeSecureValue($valueToSign, $secretValue = null)
    {
        return $valueToSign . self::SEPARATOR . self::hashString($valueToSign, $secretValue);
    }

    /**
     * validate signed value
     * @param string $valueToValidate
     * @param string $secretValue additional sign secret
     * @return mixed
     */
    static function checkSecureValue($valueToValidate, $secretValue = null)
    {

        $value = explode(self::SEPARATOR, $valueToValidate);

        if (count($value) != 2) {
            return;
        }

        $value = $value[0];

        if ($valueToValidate == self::makeSecureValue($value, $secretValue)) {
            return $value;
        }
    }

}