heres my php code to execute the post. The form works except for when I click submit. It opens a blank page titled index.php. Also I put the php file in the js folder hence the extension.
<!DOCTYPE html>
<html>
<head>
    <title>sending an email</title>
</head>
<body>
<?php
if(isset($_POST['email'])) {
    // EDIT THE 2 LINES BELOW AS REQUIRED
    $email_to = "myemail@gmail.com";
    $email_subject = "PORTFOLIO MESSAGE";
    function died($error) {
        // your error code can go here
        echo "We are very sorry, but there were error(s) found with the form you submitted. ";
        echo "These errors appear below.<br /><br />";
        echo $error."<br /><br />";
        echo "Please go back and fix these errors.<br /><br />";
        die();
    }
    // validation expected data exists
    if(!isset($_POST['name']) ||
        !isset($_POST['mail']) ||
        !isset($_POST['subject']) ||
        !isset($_POST['message'])) {
        died('We are sorry, but there appears to be a problem with the form you submitted.');       
    }
    $name = $_POST['name']; // required
    $email_from = $_POST['mail']; // required
    $subject = $_POST['subject']; // not required
    $comments = $_POST['message']; // required
    $error_message = "";
    $email_exp = '/^[A-Za-z0-9._%-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$/';
  if(!preg_match($email_exp,$email_from)) {
    $error_message .= 'The Email Address you entered does not appear to be valid.<br />';
  }
    $string_exp = "/^[A-Za-z .'-]+$/";
  if(!preg_match($string_exp,$name)) {
    $error_message .= 'The Name you entered does not appear to be valid.<br />';
  }
  if(strlen($comments) < 2) {
    $error_message .= 'The message you entered do not appear to be valid.<br />';
  }
  if(strlen($error_message) > 0) {
    died($error_message);
  }
    $email_message = "Form details below.\n\n";
    function clean_string($string) {
      $bad = array("content-type","bcc:","to:","cc:","href");
      return str_replace($bad,"",$string);
    }
    $email_message .= "Name: ".clean_string($name)."\n";
    $email_message .= "Email: ".clean_string($email_from)."\n";
    $email_message .= "Subject: ".clean_string($subject)."\n";
    $email_message .= "Message ".clean_string($comments)."\n";
// create email headers
$headers = 'From: '.$email_from."\r\n".
'Reply-To: '.$email_from."\r\n" .
'X-Mailer: PHP/' . phpversion();
@mail($email_to, $email_subject, $email_message, $headers);  
?>
<!-- include your own success html here -->
Thank you for contacting us. We will be in touch with you very soon.
<?php
}
?>
</body>
</html>
and here is my HTML to set up the form
<div class="inner contact">
                <!-- Form Area -->
                <div class="contact-form">
                    <!-- Form -->
                    <form id="contact-us" method="post" action="js/index.php">
                        <!-- Left Inputs -->
                        <div class="col-xs-6 wow animated slideInLeft" data-wow-delay=".5s">
                            <!-- Name -->
                            <input type="text" name="name" id="name" required="required" class="form" placeholder="Name" />
                            <!-- Email -->
                            <input type="email" name="mail" id="mail" required="required" class="form" placeholder="Email" />
                            <!-- Subject -->
                            <input type="text" name="subject" id="subject" required="required" class="form" placeholder="Subject" />
                        </div><!-- End Left Inputs -->
                        <!-- Right Inputs -->
                        <div class="col-xs-6 wow animated slideInRight" data-wow-delay=".5s">
                            <!-- Message -->
                            <textarea name="message" id="message" class="form textarea"  placeholder="Message"></textarea>
                        </div><!-- End Right Inputs -->
                        <!-- Bottom Submit -->
                        <div class="relative fullwidth col-xs-12">
                            <!-- Send Button -->
                            <button type="submit" id="submit" name="submit" class="form-btn semibold">Send Message</button> 
                        </div><!-- End Bottom Submit -->
                        <!-- Clear -->
                        <div class="clear"></div>
                    </form>
                    <!-- Your Mail Message -->
                    <div class="mail-message-area">
                        <!-- Message -->
                        <div class="alert gray-bg mail-message not-visible-message">
                            <strong>Thank You !</strong> Your email has been delivered.
                        </div>
                    </div>
                </div><!-- End Contact Form Area -->
            </div><!-- End Inner -->
