Creating a simple captcha system with PHP

Creating a simple captcha system with PHP

Here's a simple method to create a captcha code with Javascript.

The code is quite easy to figure out and works with any TTF font that you might want to use. You can add more or less noise on the image, as you wish. You can also hard-code other colors in the code. Here's the code:

class.funkycaptcha.php

COD:
 class FunkyCaptcha { 
   
    var $font = 'arial.ttf'; 
    var $char_list = '23456789abcdefghjkmnprstvwxyz'; 
     
    // Set character list 
    function setCharlist($list) { 
         $this->char_list = $list; 
                     } 
     
    // Set font
    function setFont($fontname) { 
         $this->font = $fontname; 
    } 
      
    // Return a random code of $characters length 
    function CaptchaCode($characters) { 
       $captcha = substr(str_shuffle($this->char_list), 0, $characters); 
       return $captcha; 
    } 
      
    // Return the captcha image and store the code and the IP session 
    function CreateCaptcha($width='120',$height='40',$characters='6', $dotnoise='80', $linenoise='80') { 
       $error = ""; 
       $code = $this->CaptchaCode($characters); 
   
       $font_size = $height * 0.60; 
       $image = imagecreate($width, $height); 
       
       $background_color = imagecolorallocate($image, 255, 255, 255); 
       $text_color = imagecolorallocate($image, 0, 0, 0); 
       $noise_color = imagecolorallocate($image, 255, 255, 255); 
         
       $textbox = imagettfbbox($font_size, 0, $this->font, $code); 
       $x = ($width - $textbox[4])/2; 
       $y = ($height - $textbox[5])/2; 
         
       imagettftext($image, $font_size, 0, $x-10, $y, $text_color, $this->font , $code); 
         
       $dotnoise = abs($dotnoise-100); 
       $linenoise = abs($linenoise-100); 
         
       if ($dotnoise == 0) $dotnoise = 1;
       if ($linenoise == 0) $linenoise = 1; 
   
       $dot_ratio = ($dotnoise/100) * ($width*$height); 
       $line_ratio = ($linenoise/100) * ($width*$height); 
         
       for( $i=0; $i<($width*$height)/$dot_ratio; $i++ ) {               
          imagefilledellipse($image, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color); 
       } 
        
       for( $i=0; $i<($width*$height)/$line_ratio; $i++ ) { 
          imageline($image, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width), mt_rand(0,$height), $noise_color); 
       } 
         
       if ($error != "") { 
         echo "$error"; 
         die(); 
       } 
       $_SESSION['captcha'] = $code; 
         if (isset($_SERVER['REMOTE_ADDR'])) { 
             $_SESSION['ipcheck'] = $_SERVER['REMOTE_ADDR']; 
             $_SESSION['code'] = $code;   
                              } else { 
             $_SESSION['ipcheck'] = 'notset'; 
             $_SESSION['code'] = 'notset';
                                  } 
           
                        ob_end_clean(); 
           header('Content-Type: image/jpeg'); 
           imagejpeg($image); 
           imagedestroy($image); 
           exit; 
    } 
 }

To use it, just like in the example above, here's a short example:

Creating the image

COD:
 session_start(); 
 require_once($_SERVER['DOCUMENT_ROOT']."/php/class.funkycaptcha.php"); 
 $captcha = new FunkyCaptcha(); 
   
 $captcha->setFont($_SERVER['DOCUMENT_ROOT'].'/demos/funkycaptcha/arial.ttf'); 
 $captcha->CreateCaptcha(150, 30, 5);

Using the image in a form

COD:
 <?php 
    session_start(); 
 ?> 
   
 <img src="captcha.php" /> 
 <br> 
 <form name="captcha" action="" method="post">
    <input type="text" name="captcha" /> 
    <input type="submit" name="send" value="send" />  
 </form>
   
 <?php 
    if (isset($_POST['captcha'])) { 
        if ($_POST['captcha'] == $_SESSION['code']) { 
            echo " 
                Pass 
                <pre>
            "; 
            print_r($_SESSION); 
            echo " 
                </pre> 
            "; 
        } else { 
            echo "Fail"; 
        } 
    } 
 ?>

The code in this article is distributed under the MIT license

You can visit the author's website at blog.hazardousgaming.info

Click here if you want to see other articles by the same author

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