core-bundle/src/Resources/contao/forms/FormCaptcha.php
protected function generateCaptcha()
	{
		if ($this->arrCaptcha)
		{
			return;
		}

		$int1 = random_int(1, 9);
		$int2 = random_int(1, 9);

		$this->arrCaptcha = array
		(
			'int1' => $int1,
			'int2' => $int2,
			'sum' => $int1 + $int2,
			'key' => $this->strCaptchaKey,
			'hashes' => $this->generateHashes($int1 + $int2)
		);
	}
protected function generateCaptcha()
	{
		if ($this->arrCaptcha)
		{
			return;
		}

		$int1 = random_int(1, 9);
		$int2 = random_int(1, 9);

		$this->arrCaptcha = array
		(
			'int1' => $int1,
			'int2' => $int2,
			'sum' => $int1 + $int2,
			'key' => $this->strCaptchaKey,
			'hashes' => $this->generateHashes($int1 + $int2)
		);
	}
Generate the captcha values