getCaptcha

 public function getCaptcha()
{
    $letters = '4783abcdefGKIJKLMNOPQRSTUVWXYZ';
    $caplen = 6;
    $width = 120;
    $height = 20;
    $font = 'ComicSpans.ttf';
    $fontsize = 14;

    header('Content-type: image/png');

    $im = imagecreatetruecolor($width, $height);
    imagesavealpha($im, true);
    $bg = imagecolorallocatealpha($im, 0, 0, 0, 127);
    imagefill($im, 0, 0, $bg);

    putenv('GDFONTPATH=' . realpath('.'));

    $captcha = '';
    for ($i = 0; $i < $caplen; $i++) {
        $captcha .= $letters[rand(0, strlen($letters) - 1)];
        $x = ($width - 20) / $caplen * $i + 10;
        $x = rand($x, $x + 4);
        $y = $height - (($height - $fontsize) / 2);
        $curcolor = imagecolorallocate($im, rand(0, 100), rand(0, 100), rand(0, 100));
        $angle = rand(-25, 25);
        imagettftext($im, $fontsize, $angle, $x, $y, $curcolor, $font, $captcha[$i]);
    }
}