Simple PHP Captcha

0-PHP-CAPTCHA.MD

PHP CAPTCHA

https://code-boxx.com/simple-php-captcha-script/

IMAGES

NOTES

1. Please enable the GD extension extension=gd (gd2 prior to PHP8) in php.ini.
2. Change the captcha font $capF in 1-captcha.php to your own.
3. Launch 2-form.php in your browser, that's all.

LICENSE

Copyright by Code Boxx

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

1-captcha.php

<?php
class Captcha {
  // (A) CAPTCHA SETTINGS
  private $length = 8; // number of characters
  private $capW = 300; // captcha width
  private $capH = 100; // captcha height
  private $capF = "C:/Windows/Fonts/arial.ttf"; // font - CHANGE TO YOUR OWN!
  private $capFS = 24; // captcha font size
  private $capB = __DIR__ . DIRECTORY_SEPARATOR . "CapBack.jpg"; // background image

  // (B) AUTO START SESSION
  function __construct () {
    if (session_status()==PHP_SESSION_DISABLED) { exit("Sessions disabled"); }
    if (session_status()==PHP_SESSION_NONE) { session_start(); }
  }

  // (C) PRIME THE CAPTCHA - GENERATE RANDOM STRING IN SESSION
  function prime () : void {
    $char = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    $max = strlen($char) - 1;
    $_SESSION["captcha"] = "";
    for ($i=0; $i<=$this->length; $i++) { $_SESSION["captcha"] .= substr($char, rand(0, $max), 1); }
  }

  // (D) DRAW THE CAPTCHA IMAGE
  function draw ($mode=0) : void {
    // (D1) FUNKY BACKGROUND IMAGE
    if (!isset($_SESSION["captcha"])) { exit("Captcha not primed"); }
    $captcha = imagecreatetruecolor($this->capW, $this->capH);
    list($bx, $by) = getimagesize($this->capB);
    $bx = ($bx-$this->capW) < 0 ? 0 : rand(0, ($bx-$this->capW));
    $by = ($by-$this->capH) < 0 ? 0 : rand(0, ($by-$this->capH));
    imagecopy($captcha, imagecreatefromjpeg($this->capB), 0, 0, $bx, $by, $this->capW, $this->capH);

    // (D2) RANDOM TEXTBOX POSITION
    $ta = rand(-20, 20); // random angle
    $tc = imagecolorallocate($captcha, rand(120, 255), rand(120, 255), rand(120, 255)); // random text color
    $ts = imagettfbbox($this->capFS, $ta, $this->capF, $_SESSION["captcha"]);
    if ($ta>=0) {
      $tx = rand(abs($ts[6]), $this->capW - (abs($ts[2]) + abs($ts[6])));
      $ty = rand(abs($ts[5]), $this->capH);
    } else {
      $tx = rand(0, $this->capW - (abs($ts[0]) + abs($ts[4])));
      $ty = rand(abs($ts[7]), abs($ts[7]) + $this->capH - (abs($ts[3]) + abs($ts[7])));
    }
    imagettftext($captcha, $this->capFS, $ta, $tx, $ty, $tc, $this->capF, $_SESSION["captcha"]);

    // (D3) OUTPUT CAPTCHA
    if ($mode==0) {
      ob_start();
      imagepng($captcha);
      $ob = base64_encode(ob_get_clean());
      echo "<img src='data:image/png;base64,$ob'>";
    } else {
      header("Content-type: image/png");
      imagepng($captcha); imagedestroy($captcha);
    }
  }

  // (E) VERIFY CAPTCHA
  function verify ($check) {
    if (!isset($_SESSION["captcha"])) { exit("Captcha not primed"); }
    if ($check == $_SESSION["captcha"]) {
      unset($_SESSION["captcha"]);
      return true;
    } else { return false; }
  }
}

// (F) CAPTCHA OBJECT
$PHPCAP = new Captcha();

2-form.php

<!DOCTYPE html>
<html>
  <head>
    <title>PHP Captcha Demo</title>
    <meta charset="utf-8">
    <link rel="stylesheet" href="x-dummy.css">
  </head>
  <body>
    <form method="post" action="3-submit.php">
      <!-- (A) FORM FIELDS -->
      <label>Name</label>
      <input name="name" type="text" required value="Jon Doe">
      <label>Email</label>
      <input name="email" type="email" required value="jon@doe.com">

      <!-- (B) CAPTCHA HERE -->
      <label>Are you human?</label>
      <?php
      require "1-captcha.php";
      $PHPCAP->prime();
      $PHPCAP->draw();
      ?>
      <input name="captcha" type="text" required>

      <!-- (C) GO! -->
      <input type="submit" value="Go!">
    </form>
  </body>
</html>

3-submit.php

<?php
// (A) LOAD CAPTCHA LIBRARY
require "1-captcha.php";

// (B) VERIFIED - DO SOMETHING
if ($PHPCAP->verify($_POST["captcha"])) {
  $result = "Congrats, CAPTCHA is correct.";
  print_r($_POST);
}

// (C) NOPE
else { echo "CAPTCHA does not match!"; }

x-dummy.css

/* (X) NOT IMPORTANT - COSMETICS */
* {
  font-family: Arial, Helvetica, sans-serif;
  box-sizing: border-box;
}
form {
  max-width: 400px;
  padding: 15px;
  border: 1px solid #efefef;
  background: #f5f5f5;
}
label, input {
  display: block;
  width: 100%;
}
label {
  margin: 10px 0;
}
label:first-child { margin-top: 0; }
input {
  padding: 10px;
  border: 1px solid #e5e5e5;
}
img {
  display: block;
  margin: 10px auto;
}
input[type=submit] {
  margin-top: 20px;
  border: 0;
  color: #fff;
  background: #3c58bf;
  cursor: pointer;
}