If you need to spam protect your contact, comment or any other public form you should think about using a CAPTCHA image. A CAPTCHA image is an image with a random text which spam bots can’t read. The visitor need to enter that text into a form field and only if there is a match the form get processed.

Try a search for “CAPTCHA image” on Google and you will find a lot of scripts, some of them are powerful and some of them are not very effective. I’m using reCAPTCHA since several years, their challenge image is very effective and safe and if people can’t read it they can listen to an audio file.

I’m sure you have seen this image before, this is the challenge image you get with their default configuration. if you don’t like this huge RED image (like me) you need a custom theme. The good news is they offer a very powerful API system for the client side and also for the server side. In this tutorial we use some jQuery code together with the reCAPTCHA ajax library to generate the challenge images. The validation process is done by a PHP script that use a simple cURL function to submit the request and response to the reCAPTCHA server to test the submitted match. We use also the jQuery form plugin to process the form fields and client side validation.

If you like to see how it looks like check this custom CAPTCHA theme demo page.

reCAPTCHA client side script

Before we start we need to register a domain name at the reCAPTCHA website to receive a public and private key. To create a custom challenge image the Ajax way, we need to include the external file recaptcha_ajax.js and we use the following JavaScript code:

var RecaptchaOptions = {
	theme : 'custom'
};
Recaptcha.create('your public key', 'recaptcha_image', RecaptchaOptions);
Recaptcha.focus_response_field();

There is only one option required for this custom function, check this link if you like to set more options.
Next we need a small HTML snippet to show the challenge image:

<div id="recaptcha_image"></div>
<p>
	<input type="text" name="recaptcha_response_field" id="recaptcha_response_field" size="30" />
	<input type="submit" value="Submit" id="submit_button" /> 
</p>

To get this working you need to create a form text field with the name and ID recaptcha_response_field, use the same ID name of the target DIV container as you used in the JavaScript function. Using both snippets in used in a HTML page will generate a neutral CAPTCHA image like:

The current code doesn’t process our CAPTCHA validation script. We do this using jQuery and the jQuery form plugin. In this tutorial we do not explain how the plugin works, we did that already in this jQuery form plugin tutorial. In the next JavaScript snippet we check if the text field is not empty and if there is a response we hide the form and show the response in the DIV container output.

$(document).ready(function() { 
	var options = { 
        target:        '#output',   // target element(s) to be updated with server response 
        beforeSubmit:  showRequest,  // pre-submit callback 
        success:       showResponse,  // post-submit callback 
        url:       'recaptcha.php'  // override for form's 'action' attribute 
    }; 
    $('#myform').submit(function() { 
        $(this).ajaxSubmit(options); 
        return false; 
    });
	var RecaptchaOptions = {
		theme : 'custom'
	};
 	Recaptcha.create('your public key', 'recaptcha_image', RecaptchaOptions);
}); 
// pre-submit callback 
function showRequest(formData, jqForm, options) { 
	var resp_field = $('input[name=recaptcha_response_field]').fieldValue();
	if (!resp_field[0]) { 
		alert('You need to enter the validation string.'); 
		return false; 
	} 
} 
// post-submit callback 
function showResponse(responseText, statusText)  { 
    if (statusText == 'success' && responseText != '') {
    	$('#formcont').html(''); 
	} else {
		alert('Error while processing your request\nPlease try it again on a later moment.'); 
	}
}

Server side validation script

Next we need to create a PHP script called recaptcha.php that will validate the entered text from our CAPTCHA image.

if (!empty($_POST['recaptcha_response_field'])) {
	$answer = trim(stripslashes($_POST['recaptcha_response_field']));
	$postData['challenge'] = $_POST['recaptcha_challenge_field'];	
	$postData['response'] = urlencode($answer);
	$postData['remoteip'] = $_SERVER['REMOTE_ADDR'];
	$postData['privatekey'] = 'your private key';
	$ch = curl_init("http://api-verify.recaptcha.net/verify");
	curl_setopt($ch, CURLOPT_POSTFIELDS, $postData);
	curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
	$data = curl_exec($ch);
	curl_close($ch);
	$response = explode(PHP_EOL, $data);
	if ($response[0] == 'true') {
		echo 'Success, you may proceed!';
	} else {
		echo 'Error, please try again.';
		// check the API documentation for detailed error reports
	}
}

In this script we create a post array for the cURL function and post all the data to the reCAPTCHA API URL. Note all used variables are required, the post variable recaptcha_challenge_field is generated by the client API. The value for the challenge entry need to be encoded before we can post that value to the reCAPTCHA API. After we received the response we split the string and check if the first part is equal to true and output a success or error message which is presented in the target DIV container.

If you like to use this script on your own website feel free to download the script on our PHP script forum.Similar Posts:

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The past months I used the jQuery form plugin in several projects. Most forms were contact or feedback forms and some of them did a file upload as well. In a previous tutorial we explained how-to create a sign-up form for MailChimp. This sign-up form is a great example to use the jQuery form plugin as well.

What do you get in this tutorial

• First we investigate the form plugin a little bit and explain some interesting features
• With this knowledge in mind we will showcase some of the plugin’s functions
• Finally we provide examples on how-to use the form plugin for simple forms with different response methods

Example files for the Ajax form (HTML and PHP)

In this tutorial we use a simple form (example.php) that will post an email address and is able to upload one file. Below this form there is a container called #output, this DIV element is used to show the response from the process.php file.

<div id="container">
	<form action="process.php" method="post" id="my-form" enctype="multipart/form-data">
		<p>E-mail<br />
		<input type="text" name="email" id="email" /></p>
		<p>File<br />
		<input type="file" name="upload" id="upload" /></p>
		<p><input type="submit" value="Submit" /></p>
	</form>
</div>
<div id="output"></div>

Our PHP example (process.php) has only two main functions; validate the email address entry and test/process the file upload. To make this example more clear, we show only some information extracted from the uploaded file. If you need a full featured upload function, you should try this PHP upload class.

if (isset($_POST['email'])) {	
	if (preg_match('(\w[-._\w]*\w@\w[-._\w]*\w\.\w{2,})', $_POST['email'])) {
		$msg = 'E-mail address is valid';
	} else {
		$msg = 'Invalid email address';
	}
	if ($_FILES['upload']['error'] > 0) {
  		$upl = '<br />Error: ' . $_FILES['upload']['error'] . '<br />';
    } else {
		$upl = '<br />Upload: ' . $_FILES['upload']['name'] . '<br />';
		$upl .= 'Type: ' . $_FILES['upload']['type'] . '<br />';
		$upl .= 'Size: ' . ($_FILES['upload']['size'] / 1024) . ' Kb<br />';
		$upl .= 'Stored in: ' . $_FILES['upload']['tmp_name'];
  	}
	echo $msg.$upl; // output the result
} else {
	die('Invalid entry!');
}

Using the form plugin is easy!

To process our form the Ajax style with the jQuery plugin, we need only some simple JavaScript code. Add the following code into the header section from your example.php file:

<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="jquery.form.js"></script>
<script type="text/javascript">
$(document).ready(function() { 
    var options = { target: '#output' }; 
    $('#my-form').submit(function() { 
        $(this).ajaxSubmit(options); 
        return false; 
    });
}); 
</script>

Running this script will process your form without to reload the page in your browser and as the result you get some information below your form. Before we change our example to have a more advanced web form, we explain the most important options and features for the jQuery form plugin.

ajaxForm and ajaxSubmit Options

The plugin has two methods to process a form, we use for this tutorial only the submit type. For the simple example above we used already the option named target, you need this option if you don’t use the success handler option and if you use the default data type. If you like to do some client side form validation the option beforeSubmit should be used. Both options success and beforeSubmit are callback functions, create custom functions for custom functionality. There are several supported data types for the response: XML, JSON or Script. If you leave the option dataType empty the response is just HTTP data. There are more options, check the Options tab from the plugin resource site.

Client side form validations

The option beforeSubmit makes it possible to create a custom function to validate our form before the data is submitted to the process.php script. Using the following function we test if the field email if one is not empty.

function showRequest(formData, jqForm, options) { 
	var form = jqForm[0];
	// or use 
	// if (!$('input[@name=email]').fieldValue()) { 
	if (!form.email.value) { 
		$('#output').html('Email address is empty!'); 
		return false; 
	} else {	    		
		return true;
	}
}

We use the plugin’s native array jqForm to identify the email field. As an alternative it’s possible to access the field via the function fieldValue. Next we need to enable the option beforeSubmit before the function call:

$(document).ready(function() { 
    var options = { target: '#output', beforeSubmit: showRequest }; 
    $('#my-form').submit(function() { 
        $(this).ajaxSubmit(options); 
        return false; 
    });
});

Using our example now, we get an error message if we left the email field empty, note this happens without a request to the server!

Advanced response handling

In our last example we want to change the way how the response will show up in our small application. After the form is submitted we want to remove the form and show some alternative header plus the data we get from the server. We split the data in two parts: the message and the file information from the file we have uploaded. First we change the process.php file a little bit, replace code echo $msg.$upl; with the following code:

echo '
<xml>
	<someText>'.$msg.'</someText>
	<uploadInfo>'.$upl.'</uploadInfo>
</xml>';

We create here XML nodes to hold the two strings, which we will access later from the custom response callback function.

function showResponse(responseText, statusText)  { 
	if (statusText == 'success') {
		$('#container').html('<h3>Some title</h3>'); 
		$('#output').html('<p>' + $('someText', responseText).text()  + '</p><div>' + $('uploadInfo', responseText).html() + '</div>'); 
	} else {
		alert('status: ' + statusText + '\n\nSomething is wrong here');
	}
}

We added also a test for the statusText and some title header element. The header is a replacement for the form, to make it more clear when the form is submitted. The message and the info takes place in two different HTML elements.

Now we have a a simple Ajax upload form with form validation (client and server side), where the server response is placed in detailed HTML elements. Based on our example it’s possible to make the small application much bigger with more functions on the client side and the server side. I hope this tutorial has helped to understand how-to create an jQuery/Ajax form powered by the jQuery Form Plugin. If you have questions or if you like to show-case your own forms, of course based on this tutorial or similar examples, please feel free to post your message below. Please don’t spam, we moderate all comment submissions.Similar Posts:

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