I would like to add captcha to my registration system. I searched google and i get some. There are more number of scripts in that which are little bit complex to go on. I simply took my needs from that. Now My registration page is generating captcha, but i dont know how to check it back after the user enters from the shown image.
Here's my coding.
Captcha.php
<?php
session_start();
//Settings: You can customize the captcha here
$image_width = 120;
$image_height = 40;
$characters_on_image = 6;
$font = './monofont.ttf';
//The characters that can be used in the CAPTCHA code.
//avoid confusing characters (l 1 and i for example)
$possible_letters = '23456789bcdfghjkmnpqrstvwxyz';
$random_dots = 0;
$random_lines = 20;
$captcha_text_color="0x142864";
$captcha_noice_color = "0x142864";
$code = '';
$i = 0;
while ($i < $characters_on_image) {
$code .= substr($possible_letters, mt_rand(0, strlen($possible_letters)-1), 1);
$i++;
}
$font_size = $image_height * 0.75;
$image = @imagecreate($image_width, $image_height);
/* setting the background, text and noise colours here */
$background_color = imagecolorallocate($image, 255, 255, 255);
$arr_text_color = hexrgb($captcha_text_color);
$text_color = imagecolorallocate($image, $arr_text_color['red'],
$arr_text_color['green'], $arr_text_color['blue']);
$arr_noice_color = hexrgb($captcha_noice_color);
$image_noise_color = imagecolorallocate($image, $arr_noice_color['red'],
$arr_noice_color['green'], $arr_noice_color['blue']);
/* generating the dots randomly in background */
for( $i=0; $i<$random_dots; $i++ ) {
imagefilledellipse($image, mt_rand(0,$image_width),
mt_rand(0,$image_height), 2, 3, $image_noise_color);
}
/* generating lines randomly in background of image */
for( $i=0; $i<$random_lines; $i++ ) {
imageline($image, mt_rand(0,$image_width), mt_rand(0,$image_height),
mt_rand(0,$image_width), mt_rand(0,$image_height), $image_noise_color);
}
/* create a text box and add 6 letters code in it */
$textbox = imagettfbbox($font_size, 0, $font, $code);
$x = ($image_width - $textbox[4])/2;
$y = ($image_height - $textbox[5])/2;
imagettftext($image, $font_size, 0, $x, $y, $text_color, $font , $code);
/* Show captcha image in the page html page */
header('Content-Type: image/jpeg');// defining the image type to be shown in browser widow
imagejpeg($image);//showing the image
imagedestroy($image);//destroying the image instance
$_SESSION['6_letters_code'] = $code;
function hexrgb ($hexstr)
{
$int = hexdec($hexstr);
return array("red" => 0xFF & ($int >> 0x10),
"green" => 0xFF & ($int >> 0x8),
"blue" => 0xFF & $int);
}
?>My Registration Page
<html>
<head>
<title>Register Page</title>
<script type="text/javascript" language="javascript">
function refreshCaptcha()
{
var img = document.images['captchaimg'];
img.src = img.src.substring(0,img.src.lastIndexOf("?"))+"?rand="+Math.random()*1000;
}
</script>
</head>
<body>
<table width="100%" border="1">
<form method="POST" action="chkregister.php">
<tr>
<td>Enter Username:</td>
<td><input type="text" id="regusrname" name="regusrname" /></td>
<td id="v1"> </td>
</tr>
<tr>
<td>Enter Password:</td>
<td><input type="text" id="regusrpwd" name="regusrpwd" /></td>
<td id="v2"> </td>
</tr>
<tr>
<td>Confirm Password:</td>
<td><input type="text" id="regcusrpwd" /></td>
<td id="v3"> </td>
</tr>
<tr>
<td>Enter Email Address:</td>
<td><input type="text" id="email" name="email" /></td>
<td id="v4"> </td>
</tr>
<tr>
<td>Enter the image shown below:</td>
<td><input type="text" id="6_letters_code" name="6_letters_code" /></td>
<td> </td>
</tr>
<tr>
<td> </td>
<td><img src="captcha.php?rand=<?php echo rand(); ?>" id='captchaimg' /></td>
<td><small>click <a href='javascript: refreshCaptcha();'>here</a> to refresh</small></td>
</tr>
<tr>
<td colspan="3"><input type="submit" value="Register" /></td>
</tr>
</form>
</table>
</body>
<html>