ajaxsignup.js

// <h3>Join Our Mailing List</h3>
// 
// <div id="theForm">
//     <form action="http://inmunited.createsend.com/t/r/s/tdfly/" method="post" id="subForm">
//         <input type="text" class="text" name="cm-tdfly-tdfly" placeholder="Email Address" id="tdfly-tdfly" />
//         <input type="submit" class="submit" value="GO" />
//     </form>
// </div>
// <div id="confirmation">
//     Thanks for subscribing!
// </div>


$('#subForm').ajaxSignup({
    campaign_monitor_id: 'tdfly',
    wp_theme_url: '/wp-content/themes/clsc'
});


$.fn.ajaxSignup = function(settings) {
    var config = {
        messages: {
            invalidEmail: 'Please enter a valid email address',
            serverFail: 'The email address you supplied is invalid and needs to be fixed before you can subscribe to this list.'
        }
    };
    // allow custom settings to passed in
    if (settings) $.extend(config, settings);

    return this.each(function(){
        // cachin' some vars
        var $form       = $(this).parent('form'),
        $form_div       = $("#theForm"), 
        $confirmation   = $('#confirmation');
        action          = $form.attr('action'),
        id              = config.campaign_monitor_id,
        emailId = id + "-" + id;

        $(this).bind('submit', function(e) {                
            e.preventDefault();
                // check for email validation
            if (!checkEmail(emailId)) { alert(config.messages.invalidEmail); return; }
            var str = $form.serialize();
            var serialized = str + "&action=" + action;
            $.ajax({
                url: config.wp_theme_url + "/proxy.php",
                type: "POST",
                data: serialized,
                success: function(data){
                    if (data.search(/invalid/i) != -1) {
                        alert(config.messages.serverFail);
                    } else {
                        $form_div.hide(); 
                        $confirmation.slideDown("slow");  
                        $confirmation.tabIndex = -1;
                        $confirmation.focus(); 
                    }
                }
            });

        });          
    });
    
    function checkEmail(email) {	
        var pattern = /^([a-zA-Z0-9_\.\-\+])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
        var emailVal = $("#" + email).val();
        return pattern.test(emailVal);
    }
};

proxy.php

<?php
header('Content-type: text/javascript');

// Extract form action and assign to variable

	$action = $_POST['action'];

// Assign form array to single variable

	$arr = $_POST;

// Remove "action" key from array

	unset($arr['action']); 

// Loop through and add keys and values to a single variable

	foreach ($arr as $key => $value) {
		
		if (is_array($value))
		{
			
			foreach ($value as $subvalue) {
				$formVars .= $key."=".urlencode($subvalue)."&";
			}

		}
		else
		{
			$formVars .= $key."=".urlencode($value)."&";
		}
	}

// Remove last "&"

	$formVars = substr($formVars,0,-1);

// Get the response

	$handle = curl_init($action);

// If there is something, read and return

	curl_setopt($handle, CURLOPT_POST, true);
	curl_setopt($handle, CURLOPT_POSTFIELDS, $formVars);
	curl_setopt ($handle, CURLOPT_FOLLOWLOCATION, 1);
	echo curl_exec($handle);
	curl_close($handle);
?>