Captcha Generator using PHP

Submitted by jaredgwapo on Wednesday, January 13, 2016 - 10:50.

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In this tutorial we are going to learn how to make a captcha generator that you can use in login, sign up, comment and etc. Just download the source code below.

DIRECTIONS

Create index.php

<?php
session_start();
$_SESSION = array();
 
include("simple-php-captcha.php");
$_SESSION['captcha'] = simple_php_captcha();
 
?>
<!DOCTYPE html>
<html>
<head>
    <title>Example &raquo; A simple PHP CAPTCHA script</title>
    <style type="text/css">
        pre {
            border: solid 1px #bbb;
            padding: 10px;
            margin: 2em;
        }
 
        img {
            border: solid 1px #ccc;
            margin: 0 2em;
        }
    </style>
</head>
<body>
    <h1>
        CAPTCHA Example
    </h1>
    <p>
        <?php
        echo '<img src="' . $_SESSION['captcha']['image_src'] . '" alt="CAPTCHA code">';
 
        ?>
    </p>
</body>
</html>

Create simple-php-captcha.php

<?php
//
//  A simple PHP CAPTCHA script
//
//  Copyright 2011 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__) . '/backgrounds/';
    $font_path = dirname(__FILE__) . '/fonts/';
 
    // 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'];
 
    // Generate CAPTCHA code if not set by user
    if( empty($captcha_config['code']) ) {
        $captcha_config['code'] = '';
        $length = mt_rand($captcha_config['min_length'], $captcha_config['max_length']);
        while( strlen($captcha_config['code']) < $length ) {
            $captcha_config['code'] .= substr($captcha_config['characters'], mt_rand() % (strlen($captcha_config['characters'])), 1);
        }
    }
 
    // Generate HTML for image src
    if ( strpos($_SERVER['SCRIPT_FILENAME'], $_SERVER['DOCUMENT_ROOT']) ) {
        $image_src = substr(__FILE__, strlen( realpath($_SERVER['DOCUMENT_ROOT']) )) . '?_CAPTCHA&amp;t=' . urlencode(microtime());
        $image_src = '/' . ltrim(preg_replace('/\\\\/', '/', $image_src), '/');
    } else {
        $_SERVER['WEB_ROOT'] = str_replace($_SERVER['SCRIPT_NAME'], '', $_SERVER['SCRIPT_FILENAME']);
        $image_src = substr(__FILE__, strlen( realpath($_SERVER['WEB_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']);
 
    // Pick random background, get info, and start captcha
    $background = $captcha_config['backgrounds'][mt_rand(0, count($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 = mt_rand( $captcha_config['angle_min'], $captcha_config['angle_max'] ) * (mt_rand(0, 1) == 1 ? -1 : 1);
 
    // Select font randomly
    $font = $captcha_config['fonts'][mt_rand(0, count($captcha_config['fonts']) - 1)];
 
    // Verify font file exists
    if( !file_exists($font) ) throw new Exception('Font file not found: ' . $font);
 
    //Set the font size.
    $font_size = mt_rand($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);
    $text_pos_x = mt_rand($text_pos_x_min, $text_pos_x_max);
    $text_pos_y_min = $box_height;
    $text_pos_y_max = ($bg_height) - ($box_height / 2);
    if ($text_pos_y_min > $text_pos_y_max) {
        $temp_text_pos_y = $text_pos_y_min;
        $text_pos_y_min = $text_pos_y_max;
        $text_pos_y_max = $temp_text_pos_y;
    }
    $text_pos_y = mt_rand($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);
 
}

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