Captcha Validation using jquery

Question

I have an application form in which i need to validate captcha using jquery. If the captcha entered is wrong then an alert box as to displayed please enter captcha again the entered captcha is wrong.. How can I do this using jquery ?? Please help me. I'm new to jquery.

Here is the code :

      $(function() {
    $("#XISubmit").click(function(){
        event.preventDefault()
        val=$('#vercode').val()
        $.ajax({
            type:"post",
            url:"verify-captcha.php",
            data:{'code':val},
            success:function(data){
               if(data=='false'){
                    alert('Re-enter Captcha, You Entered wrong captcha code')
                    $("#cap").html("<img  src='captcha_image.php'>"); }
                else{  
                     document.getElementById("XIForm").submit();
                }
            }

        });    
    });
});


                document.getElementById("XIForm").submit();

                    });

**Html page :**

    <label>Security Validation</label>    

    <span><img   src="captcha_image.php"></span><input type="text" name="vercode" id="vercode" size="10" style="margin-top: -1px; float: left; width: 115px; margin-right: 12px;"></li><div id="msg"></div>

**captcha_image.php**
<?
// *** CAPTCHA image generation ***
// *** http://frikk.tk ***

session_start();

// *** Tell the browser what kind of file is come'n at 'em! ***
header("Content-Type: image/jpeg");

// *** Send a generated image to the browser ***
die(create_image());

// *** Function List ***
function create_image()
{
    // *** Generate a passcode using md5
    //  (it will be all lowercase hex letters and numbers ***
    $md5 = md5(rand(0,9999));
    $pass = substr($md5, 10, 5);

    // *** Set the session cookie so we know what the passcode is ***
    $_SESSION["pass"] = $pass;

    // *** Create the image resource ***
    $image = ImageCreatetruecolor(100, 20);

    // *** We are making two colors, white and black ***
    $clr_white = ImageColorAllocate($image, 255, 255, 255);
    $clr_black = ImageColorAllocate($image, 0, 0, 0);

    // *** Make the background black ***
    imagefill($image, 0, 0, $clr_black);

    // *** Set the image height and width ***
    imagefontheight(15);
    imagefontwidth(15);

    // *** Add the passcode in white to the image ***
    imagestring($image, 5, 30, 3, $pass, $clr_white);

    // *** Throw in some lines to trick those cheeky bots! ***
    imageline($image, 5, 1, 50, 20, $clr_white);
    imageline($image, 60, 1, 96, 20, $clr_white);

    // *** Return the newly created image in jpeg format ***
    return imagejpeg($image);

    // *** Just in case... ***
    imagedestroy($image);
}
?>

verify-captcha.php

<?php
session_start(); 
if ($_POST["code"] != $_SESSION["cap_code"] || $_SESSION["cap_code"]=='')  { 
 echo 'false';
}else{
echo 'true';}

Answer 1

The steps you can to do

1. change your submit button to a button
2. on button click, call verify-captcha.php
3. if captcha is good, submit form
4. else alert error message

Here's your script modified (not tested):

$(function() {
    $("#XISubmit").click(function(){
        event.preventDefault()
        val=$('#vercode').val()
        $.ajax({
            type:"post",
            url:"verify-captcha.php",
            data:{'code':val},
            success:function(data){
               if(data=='false'){
                    alert('Re-enter Captcha, You Entered wrong captcha code')
                    $("#cap").html("<img  src='captcha.php'>"); }
                else{  
                    $("#XIForm").submit();
                }
            }

        });    
    });
});