Tuesday, 4 August 2015

PHP_Script_ for _Captcha

07:15

(1)First write code for  "captcha.php"   file:

<?php
// Create our image
$image = imagecreatetruecolor(100, 30);

// Assign a background colour. I have set it to white but background is going to be transparent anyway
$background = imagecolorallocate($image, 0,0,0);

// Make background transparent by setting the colour we are going to use as transparent
imagecolortransparent($image, $background);

// Fill it in with the background colour. This is required to make the background transparent
imagefilledrectangle($image, 0, 0, 199, 49, $background);

// function to generate captcha characters
function captchaChars($hash)
{
  //  Generate a 32 character string by getting the MD5 hash of the servers name with the hash added to the end.
  //  Adding the servers name means outside sources cannot just work out the characters from the hash
  $captchastr = md5($_SERVER['SERVER_NAME'] . $hash);
  return strtoupper($captchastr); // Make all our characters uppercase for clarity in the image
}

// Lets get the characters to show in the image or say 'error' if no hash submitted
$str = (!empty($_GET['hash'])) ? captchaChars($_GET['hash']) : 'ERROR';

// Assign a colour for the text and lines. I've chosen a shade of grey
$our_colour = imagecolorallocate($image, 140,140,140);

// Lets add three random background lines
for ($i = mt_rand(5, 8); $i <= 29; $i += 10)
{
  imageline($image, mt_rand(0, 100), $i + mt_rand(-5, 5), mt_rand(0, 100), $i + mt_rand(-5, 5), $our_colour);
}

// Set a random horizontal starting position
$x_pos = mt_rand(10, 20);

// Lets loop through our string adding one character at a time in a randomish position
// We start with the first character and then use every seventh character just for added randomness
for($i = 0; $i <= 28; $i += 7)
{
  imagestring($image, 5, $x_pos, mt_rand(0, 12), $str[$i], $our_colour); // add a character from our string
  $x_pos += mt_rand(10, 18);  // Move the horizontal position by a random amount
}

// Add some wavy distortion to the image
$wave = rand(3,5);
$wave_width = rand(8,15);
for ($i = 0; $i < 200; $i += 2)
{
  imagecopy($image, $image, $i - 2, sin($i / $wave_width) * $wave, $i, 0, 2, 40);
}

// Send the gif header. We use a gif because of IE6's poor support for PNG transparency
header('Content-type: image/gif');
// Dump the image
imagegif($image);

?>



(2)Second write code for   "captchaform.php"  file:


<?php
$hash = substr(md5(mt_rand(1, 1000)), 10, 20); // Just generate a random hash to use
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
  <meta http-equiv="content-type" content="text/html; charset=utf-8">
  <title></title>
  <script type="text/javascript">
  function reloadCaptcha(imageName)
  {
    var randomnumber=Math.floor(Math.random()*1001); // generate a random number to add to image url to prevent caching
    document.images[imageName].src = document.images[imageName].src + '&amp;rand=' + randomnumber; // change image src to the same url but with the random number on the end
  }
  </script>
  </head>
  <body>
<img src="captcha.php?hash=<?php echo $hash; ?>" alt="captcha" name="captchaImage"><br>
<a href="#" onclick="reloadCaptcha('captchaImage'); return false;">refresh image</a>
<form action="captchaform.php" method="post">
<input type="text" name="captchacode"><br>
<input type="submit" value="Submit Code" name="submit">
<input type="hidden" value="<?php echo $hash; ?>" name="hash">
</form>
<div style="height:20px;"> <?php
if(isset($_POST['submit']))
{
  $hash = (!empty($_POST['hash'])) ? preg_replace('/[\W]/i', '', trim($_POST['hash'])) : ''; // Remove any non alphanumeric characters to prevent exploit attempts
  $captchacode = (!empty($_POST['captchacode'])) ? preg_replace('/[\W]/i', '', trim($_POST['captchacode'])) : ''; // Remove any non alphanumeric characters to prevent exploit attempts
  // function to check the submitted captcha
  function captchaChars($hash)
  {
    //  Generate a 32 character string by getting the MD5 hash of the servers name with the hash added to the end.
    //  Adding the servers name means outside sources cannot just work out the characters from the hash
    $captchastr = strtolower(md5($_SERVER['SERVER_NAME'] . $hash));
    $captchastr2 = '';
    for($i = 0; $i <= 28; $i += 7)
    {
      $captchastr2 .= $captchastr[$i];
    }
    return $captchastr2;
  }
  if(!empty($captchacode))
  {
    if(strtolower($captchacode) == captchaChars($hash))  // We convert submitted characters to lower case then compare with the expected answer
    {
      echo '<h3>The submitted characters were correct</h3>';
    }
    else
    {
      echo '<h3>The submitted characters were WRONG!</h3>';
    }
  }
  else
  {
    echo '<h3>You forgot to fill in the code!</h3>';
  }
}
?>
</div>
  </body>
</html>


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