Nelmio\SecurityBundle\Signer::verifySignedValue PHP Method

    public function verifySignedValue($signedValue)
    {
        list($value, $signature) = $this->splitSignatureFromSignedValue($signedValue);
        $signature2 = $this->generateSignature($value);
        if (strlen($signature) !== strlen($signature2)) {
            return false;
        }
        $result = 0;
        for ($i = 0, $j = strlen($signature); $i < $j; ++$i) {
            $result |= ord($signature[$i]) ^ ord($signature2[$i]);
        }
        return 0 === $result;
    }

 public function testShouldRejectInvalidSignature()
 {
     $signer = new Signer('secret', 'sha1');
     $value = 'foobar';
     $signedValue = $signer->getSignedValue($value, 'fake signature');
     $this->assertFalse($signer->verifySignedValue($signedValue));
 }