I've created some if / else statements to get a download when a user hit click jf he fields name and email but doesn"t work for my site http://my-easy-woodworking-projects.com because it is do download without field name and email contact.php is

<?php
$field_name = $_POST['cf_name'];
$field_email = $_POST['cf_email'];
$field_message = $_POST['cf_message'];

$mail_to = '[email protected]';
$subject = 'Message from a site visitor '.$field_name;

$body_message = 'From: '.$field_name."\n";
$body_message .= 'E-mail: '.$field_email."\n";
$body_message .= 'Message: '.$field_message;

$headers = 'From: '.$field_email."\r\n";
$headers .= 'Reply-To: '.$field_email."\r\n";

$mail_status = mail($mail_to, $subject, $body_message, $headers);

if ($mail_status) { 
    echo <script>\n"

echo "var str = \"download\"; \n""
echo "document.write(str.link("http://www.myshedplans.com/12BY8SHED.pdf"));\n"  

echo "</script>\n"


}
echo
else { 
  echo  <script language="javascript" type="text/javascript">
      echo  // Print a message
    echo    alert('Message failed. Please, send an email to [email protected]');
      echo  // Redirect to some page of the site. You can also specify full URL, e.g. http://template-help.com
        window.location = 'contact_page.html';
   echo </script>

}?>