simple-php-captcha.php

<?php
//
//  A simple PHP CAPTCHA script
//
//  Copyright 2013 by Cory LaViska for A Beautiful Site, LLC.
//
//  See readme.md for usage, demo, and licensing info
//
function simple_php_captcha($config = array()) {

  // Check for GD library
  if( !function_exists('gd_info') ) {
    throw new Exception('Required GD library is missing');
  }

  $bg_path = dirname(__FILE__) . '/i/captcha/';
  $font_path = dirname(__FILE__) . '/i/captcha/';

  // Default values
  $captcha_config = array(
    'code' => '',
    'min_length' => 5,
    'max_length' => 5,
    'backgrounds' => array(
      $bg_path . '45-degree-fabric.png',
      $bg_path . 'cloth-alike.png',
      $bg_path . 'grey-sandbag.png',
      $bg_path . 'kinda-jean.png',
      $bg_path . 'polyester-lite.png',
      $bg_path . 'stitched-wool.png',
      $bg_path . 'white-carbon.png',
      $bg_path . 'white-wave.png'
    ),
    'fonts' => array(
      $font_path . 'times_new_yorker.ttf'
    ),
    'characters' => 'ABCDEFGHJKLMNPRSTUVWXYZabcdefghjkmnprstuvwxyz23456789',
    'min_font_size' => 28,
    'max_font_size' => 28,
    'color' => '#666',
    'angle_min' => 0,
    'angle_max' => 10,
    'shadow' => true,
    'shadow_color' => '#fff',
    'shadow_offset_x' => -1,
    'shadow_offset_y' => 1
  );

  // Overwrite defaults with custom config values
  if( is_array($config) ) {
    foreach( $config as $key => $value ) $captcha_config[$key] = $value;
  }

  // Restrict certain values
  if( $captcha_config['min_length'] < 1 ) $captcha_config['min_length'] = 1;
  if( $captcha_config['angle_min'] < 0 ) $captcha_config['angle_min'] = 0;
  if( $captcha_config['angle_max'] > 10 ) $captcha_config['angle_max'] = 10;
  if( $captcha_config['angle_max'] < $captcha_config['angle_min'] ) $captcha_config['angle_max'] = $captcha_config['angle_min'];
  if( $captcha_config['min_font_size'] < 10 ) $captcha_config['min_font_size'] = 10;
  if( $captcha_config['max_font_size'] < $captcha_config['min_font_size'] ) $captcha_config['max_font_size'] = $captcha_config['min_font_size'];

  // Use milliseconds instead of seconds
  srand(microtime(1) * 100);

  // Generate CAPTCHA code if not set by user
  if( empty($captcha_config['code']) ) {
    $captcha_config['code'] = '';
    $length = rand($captcha_config['min_length'], $captcha_config['max_length']);
    while( strlen($captcha_config['code']) < $length ) {
      $captcha_config['code'] .= substr($captcha_config['characters'], rand() % (strlen($captcha_config['characters'])), 1);
    }
  }

  // Generate HTML for image src
  $image_src = substr(__FILE__, strlen( realpath($_SERVER['DOCUMENT_ROOT']) )) . '?_CAPTCHA&amp;t=' . urlencode(microtime());
  $image_src = '/' . ltrim(preg_replace('/\\\\/', '/', $image_src), '/');

  $_SESSION['_CAPTCHA']['config'] = serialize($captcha_config);

  return array(
    'code' => $captcha_config['code'],
    'image_src' => $image_src
  );

}


if( !function_exists('hex2rgb') ) {
  function hex2rgb($hex_str, $return_string = false, $separator = ',') {
    $hex_str = preg_replace("/[^0-9A-Fa-f]/", '', $hex_str); // Gets a proper hex string
    $rgb_array = array();
    if( strlen($hex_str) == 6 ) {
      $color_val = hexdec($hex_str);
      $rgb_array['r'] = 0xFF & ($color_val >> 0x10);
      $rgb_array['g'] = 0xFF & ($color_val >> 0x8);
      $rgb_array['b'] = 0xFF & $color_val;
    } elseif( strlen($hex_str) == 3 ) {
      $rgb_array['r'] = hexdec(str_repeat(substr($hex_str, 0, 1), 2));
      $rgb_array['g'] = hexdec(str_repeat(substr($hex_str, 1, 1), 2));
      $rgb_array['b'] = hexdec(str_repeat(substr($hex_str, 2, 1), 2));
    } else {
      return false;
    }
    return $return_string ? implode($separator, $rgb_array) : $rgb_array;
  }
}

// Draw the image
if( isset($_GET['_CAPTCHA']) ) {

  session_start();

  $captcha_config = unserialize($_SESSION['_CAPTCHA']['config']);
  if( !$captcha_config ) exit();

  unset($_SESSION['_CAPTCHA']);

  // Use milliseconds instead of seconds
  srand(microtime(1) * 100);

  // Pick random background, get info, and start captcha
  $background = $captcha_config['backgrounds'][rand(0, count($captcha_config['backgrounds']) -1)];
  list($bg_width, $bg_height, $bg_type, $bg_attr) = getimagesize($background);

  $captcha = imagecreatefrompng($background);

  $color = hex2rgb($captcha_config['color']);
  $color = imagecolorallocate($captcha, $color['r'], $color['g'], $color['b']);

  // Determine text angle
  $angle = rand( $captcha_config['angle_min'], $captcha_config['angle_max'] ) * (rand(0, 1) == 1 ? -1 : 1);

  // Select font randomly
  $font = $captcha_config['fonts'][rand(0, count($captcha_config['fonts']) - 1)];

  // Verify font file exists
  if( !file_exists($font) ) throw new Exception('Font file not found: ' . $font);

  //Set the font size.
  $font_size = rand($captcha_config['min_font_size'], $captcha_config['max_font_size']);
  $text_box_size = imagettfbbox($font_size, $angle, $font, $captcha_config['code']);

  // Determine text position
  $box_width = abs($text_box_size[6] - $text_box_size[2]);
  $box_height = abs($text_box_size[5] - $text_box_size[1]);
  $text_pos_x_min = 0;
  $text_pos_x_max = ($bg_width) - ($box_width);
  $text_pos_x = rand($text_pos_x_min, $text_pos_x_max);
  $text_pos_y_min = $box_height;
  $text_pos_y_max = ($bg_height) - ($box_height / 2);
  $text_pos_y = rand($text_pos_y_min, $text_pos_y_max);

  // Draw shadow
  if( $captcha_config['shadow'] ){
    $shadow_color = hex2rgb($captcha_config['shadow_color']);
    $shadow_color = imagecolorallocate($captcha, $shadow_color['r'], $shadow_color['g'], $shadow_color['b']);
    imagettftext($captcha, $font_size, $angle, $text_pos_x + $captcha_config['shadow_offset_x'], $text_pos_y + $captcha_config['shadow_offset_y'], $shadow_color, $font, $captcha_config['code']);
  }

  // Draw text
  imagettftext($captcha, $font_size, $angle, $text_pos_x, $text_pos_y, $color, $font, $captcha_config['code']);

  // Output image
  header("Content-type: image/png");
  imagepng($captcha);

}