I have created a contact form for a client's website. The purpose of this form is for visitors to enter some information about themselves and once they press submit, my client receives the information via email. However, the form is being submitted without any information coming through. Just emails with no contents.

Why is the contents not being sent through? I would really appreciate some guidance!

Please see my code below:

This first bit sets the email address that you want the form to be submitted to.
You will need to change this value to a valid email address that you can access.
$webmaster_email = "me@email.com";

This bit sets the URLs of the supporting pages.
If you change the names of any of the pages, you will need to change the values here.
$feedback_page = "questionnaire1.html";
$error_page = "error_message.html";
$thankyou_page = "thank_you.html";

This next bit loads the form field data into variables.
If you add a form field, you will need to add it here.
$email_address = $_REQUEST['email_address'] ;
$name = $_REQUEST['name'] ;
$telephone = $_REQUEST['telephone'] ;
$brand = $_REQUEST['brand'] ;
$target_demo = $_REQUEST['target_demo'] ;
$describe_product = $_REQUEST['describe_product'] ;

The following function checks for email injection.
Specifically, it checks for carriage returns - typically used by spammers to inject a CC list.
function isInjected($str) {
	$injections = array('(\n+)',
	$inject = join('|', $injections);
	$inject = "/$inject/i";
	if(preg_match($inject,$str)) {
		return true;
	else {
		return false;

// If the user tries to access this script directly, redirect them to the feedback form,
if (!isset($_REQUEST['email_address'])) {
header( "Location: $feedback_page" );

// If the form fields are empty, redirect to the error page.
elseif (empty($email_address) || empty($target_demo) || empty($describe_product) || empty($telephone) || empty($brand) || empty($name)) {
header( "Location: $error_page" );

// If email injection is detected, redirect to the error page.
elseif ( isInjected($email_address) ) {
header( "Location: $error_page" );

// If we passed all previous tests, send the email then redirect to the thank you page.
else {
mail( "me@email.com", "Client Questionnaire",
  "From: $email_address" );

header( "Location: $thankyou_page" );