Question

I have a captcha script and it works good. But, I don’t know how to make it refresh.

Here’s verificationimage.php:

<?php

header('Content-type: image/jpeg');

$width = 50;
$height = 24;

$my_image = imagecreatetruecolor($width, $height);

imagefill($my_image, 0, 0, 0xFFFFFF);

// add noise
for ($c = 0; $c < 40; $c++){
    $x = rand(0,$width-1);
    $y = rand(0,$height-1);
    imagesetpixel($my_image, $x, $y, 0x000000);
    }

$x = rand(1,10);
$y = rand(1,10);

$rand_string = rand(1000,9999);
imagestring($my_image, 5, $x, $y, $rand_string, 0x000000);

setcookie('tntcon',(md5($rand_string).'a4xn'));

imagejpeg($my_image);
imagedestroy($my_image);
?>

And, the page with the form:

<label for="verif_box" style="margin-top:10px;">Image Verification:</label>

<input name="verif_box" type="text" id="verif_box" autocomplete="off" minlength="4" maxlength="5" class="text" />

<img id="captcha" src="verificationimage.php?<?php echo rand(0,9999);?>" alt="This form can't be submitted because images aren't displayed" title="Verification image, type it in the box" width="50" height="24" align="absbottom" onclick="$('#verif_box').focus();" style="cursor:pointer;" /> &nbsp; (<a href="#captcha" class="fancybox">what's this?</a>)
<br />
<br />

    <?php 
    //if the variable "wrong_code" is sent from previous page then display the error field
    if(isset($_GET['wrong_code'])){?>
    <div style="border:1px solid #990000; background-color:#D70000; color:#FFFFFF; padding:4px; padding-left:6px;width:295px;">The code you entered does not match the image. Please try typing what you see in the image to the right again.</div><br /> 
    <?php ;} ?>

Here is what happens in mailer.php:

// check to see if verificaton code was correct
if(md5($verif_box).'a4xn' == $_COOKIE['tntcon']){
    // if verification code was correct send the message and show this page

    mail("[e-mail]", 'New WeeBuild Support Ticket: '.$subject, $emailContent, $headers);

    mail($email, 'Thank you for contacting WeeBuild Support! (#'.$ticket.')', $emailContents, $headers2);

    // add to database

    $today = getdate();
        $theDate = $today["weekday"].", ".$today["month"]." ".$today["mday"].", ".$today["year"];

    mysql_select_db("database_name", $con);
        $sql="INSERT INTO table_name (name, email, subject, message, ticket, ip_address, created)
        VALUES ('$_POST[name]','$_POST[email]','$_POST[subject]','$_POST[message]','$ticket','$_SERVER[REMOTE_ADDR]','$theDate')";

if (!mysql_query($sql,$con))
  {
  die('Error: ' . mysql_error());
  }

  //close the database connection
  mysql_close($con);

    // delete the cookie so it cannot sent again by refreshing this page
    setcookie('tntcon','');

} else if(isset($message) and $message!=""){

    // if verification code was incorrect then return to contact page and show error

    header("Location: index.php?name=$name&subject=$subject&email=".urlencode($email)."&message=".urlencode($message)."&wrong_code=true");
    exit;
}

It all currently works great, but how can I make the captcha refresh? I tried doing this:

<script>
$(document).ready(function() {
$('#refresh').click(function() {
$('img#captcha').attr('src','verificationimage.php?<?php echo rand(0,9999);?>');
});
});
</script>
<a href="#" id="refresh">refresh</a>

But, it doesn’t work.

By the way, I don’t want to use reCaptcha, I just rather do it this way because reCaptcha, to me, looks hard to set up with my stuff.

Answer 1

My answer is similar to the one in the comments, likely a cached copy is being used on the refresh, but it’d be cleaner to use a proper method to make sure the browser doesn’t cache that image rather than a random string. On the image generation page, add this:

header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");