Free Code Collection

A good way to avoid automatic form submissions when creating a web form is to add some kind of verification. One of the best ways is to use an image verification, called also captcha. What it does is to dynamically create an image with a random string displayed on it. Then visitor is asked to type that string in a text field and once the form is submitted it checks if the string on the image matches the one inputted by the user. Because there is no easy way to read a text from an image (image recognition) this is a good way to protect your web forms from spammers.
For doing this CAPTCHA I would suggest using a session variable where you store the string generated and displayed on that dynamically generated image.

 MySQL | 
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CREATE TABLE `comment` (
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`name` varchar(50) collate latin1_general_ci NOT NULL,
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`mail` varchar(50) collate latin1_general_ci NOT NULL,
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`url` varchar(50) collate latin1_general_ci NOT NULL,
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`comment` longtext collate latin1_general_ci NOT NULL
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)

Create a page comment.php and create form for post comments:

 HTML | 
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<form name=”commentform” action=”comments-post.php” method=”post” id=”commentform”>
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<table width=”468? border=”0? cellspacing=”3? cellpadding=”3?>
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<tr>
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<td width=”103?>Name</td>
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<td width=”344?><input name=”name” type=”text” id=”name” tabindex=”1? value=”" size=”18? /></td>
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</tr>
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<tr>
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<td>Mail</td>
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<td><input type=”text” name=”email” id=”email” value=”" size=”18? tabindex=”2? /></td>
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</tr>
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<tr>
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<td>URL</td>
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<td><input type=”text” name=”url” id=”url” value=”" size=”18? tabindex=”3? /></td>
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</tr>
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<tr>
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<td>Enter Number </td>
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<td><input name=”txtNumber” type=”text” id=”txtNumber” value=”" tabindex=”4?/>
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<img src=”randImages.php”/></td>
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</tr>
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<tr>
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<td>Comment</td>
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<td><textarea name=”comment” id=”comment” cols=”45? rows=”9? tabindex=”5?></textarea></td>
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</tr>
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<tr>
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<td>&nbsp;</td>
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<td><input name=”save” type=”submit” class=”submitbutton” id=”save” tabindex=”5? onClick=”MM_validateForm(’name’,”,’R',’email’,”,’RisEmail’,'comment’,”,’R');return document.MM_returnValue” value=”Submit Comment”/></td>
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</tr>
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</table>
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</form>

Now we will create a Image Verification Page which will show Random Images, Save this page as randImages.php.

 PHP | 
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session_start();
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// $Rand Function generate 5 digit random number starting 10000, 99999. You can Edit it as your required.
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$rand = rand(10000, 99999);
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// create the hash for the random number and put it in the session
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$_SESSION['image_random_value'] = md5($rand);
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// create the image
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$image = imagecreate(60, 30);
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// use white as the background image
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$bgColor = imagecolorallocate ($image, 255, 255, 255);
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// the text color is black
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$textColor = imagecolorallocate ($image, 0, 0, 0);
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// write the random number
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imagestring ($image, 5, 5, 8, $rand, $textColor);
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// send several headers to make sure the image is not cached
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// taken directly from the PHP Manual
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// Date in the past
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header(”Expires: Mon, 10 April 2008 05:00:00 GMT”);
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// always modified
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header(”Last-Modified: ” . gmdate(”D, d M Y H:i:s”) . ” GMT”);
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// HTTP/1.1
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header(”Cache-Control: no-store, no-cache, must-revalidate”);
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header(”Cache-Control: post-check=0, pre-check=0?, false);
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// HTTP/1.0
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header(”Pragma: no-cache”);
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// send the content type header so the image is displayed properly
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header(’Content-type: image/jpeg’);
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// send the image to the browser
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imagejpeg($image);
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// destroy the image to free up the memory
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imagedestroy($image);
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?>
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Now Create a page which insert the comment data.
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session_start();
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//Enter here your php mysql connection details
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if(isset($_POST['save'])){
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$name=$_POST['name'];
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$email=$_POST['email'];
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$url=$_POST['url'];
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$comment=$_POST['comment'];
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}
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$number = $_POST['txtNumber'];
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if (md5($number) == $_SESSION['image_random_value']) {
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$sql=”INSERT into comment(name, mail, url, comment) values(’$name’, ‘$email’, ‘$url’,
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‘$comment’)”;
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$result=mysql_query($sql) or die(’Can not Add Your Comment’);
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echo “Your Comment have been added. Returning To Write Return page here. Please wait…”;
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$_SESSION['image_random_value'] = ”;
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}
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} else {
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echo ‘Sorry, wrong Image Varification Number. Please try again’;
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}
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?>