protected $allowAnonymous = array('actionPostLead');

public function actionPostLead()
{
    $this->requireAjaxRequest();

    // Initialize the $kv array and query var for later use
    $kv = array();
    $query_string = '';

    //If there are POST variables
    if ($_POST) {

        // For each POST variable as $name_of_input_field => $value_of_input_field
        foreach ($_POST as $key => $value) {

            // Set array element for each POST variable (ie. first_name=Arsham)
            $kv[] = stripslashes($key).'='.stripslashes($value);
        }

        // Create a query string with join function separted by &
        $query_string = join('&', $kv);
    }

    // Check to see if cURL is installed ...
    if (!function_exists('curl_init')) {
        die('Sorry cURL is not installed!');
    }

    // The original form action URL from Step 2 :)
    $url = 'https://webto.salesforce.com/servlet/servlet.WebToLead?encoding=UTF-8';

    // Open cURL connection
    $ch = curl_init();

    // Set the url, number of POST vars, POST data
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_POST, count($kv));
    curl_setopt($ch, CURLOPT_POSTFIELDS, $query_string);

    // Execute SalesForce web to lead PHP cURL
    $result = curl_exec($ch);

    // close cURL connection
    curl_close($ch);

    if ($result) {
        $this->returnJson(array('success' => true));
    } else {
        $this->returnErrorJson($e->getMessage());
    }
}

$.ajax({
    type: 'POST',
    url: '/',
    data: data,
    dataType: 'json',
    success: function(response) {

        formBlock.removeClass('submitting');
        var successMessage = $('.formBlock.on').data('success-message');
        showFormSuccessBanner(successMessage);
        hideForm(id);
    },
    error: function(err) {
        console.log("Error");
        console.log(err);

        formBlock.removeClass('submitting');
    }
});