generate.php

<?php
    session_start();
    function acakCaptcha() {
        $kode = "abcdefghijklmnopqrstuwxyzABCDEFGHIJKLMNOPQRSTUWXYZ0123456789";

        $pass = array();

        $panjangkode = strlen($kode) - 2;
        for ($i = 0; $i < 5; $i++) {
            $n = rand(0, $panjangkode);
            $pass[] = $kode[$n];
        }

        return implode($pass);
    }

    //hasil kode acak disimpan di $code
    $code = acakCaptcha();

    //kode acak disimpan di dalam session agar data dapat dipassing ke halaman lain
    $_SESSION["code"] = $code;


    //membuat background
    $wh = imagecreatetruecolor(173, 50);

    $bgc = imagecolorallocate($wh, 22, 86, 165);

    //membuat text warna
    $fc = imagecolorallocate($wh, 223, 230, 233);
    imagefill($wh, 0, 0, $bgc);

    imagestring($wh, 10, 50, 15,  $code, $fc);


    //membuat gambar
    header('content-type: image/jpg');

    imagejpeg($wh);

    imagedestroy($wh);
?>