Simple WordPress Contact Form without Plugin - Bootstrap ready.

page-contact-form.php

<?php /* Template Name: Contact Page */

$response = "";

  //function to generate response
  function my_contact_form_generate_response($type, $message){

    global $response;
    if($type == "success") $response = "<div class='alert alert-success'>{$message}</div>";
    else $response = "<div class='alert alert-danger'>{$message}</div>";

  }

  //response messages
  $not_human       = "Please work out the math";
  $missing_content = "Please supply all required fields.";
  $email_invalid   = "Email Address is invalid.";
  $message_unsent  = "Message was not sent. Try Again.";
  $message_sent    = "Thank you! Your message has been sent.";

  //user posted variables
  $name = $_POST['message_name'];
  $email = $_POST['message_email'];
  $message = $_POST['message_text'];
  $human = $_POST['message_human'];

  //php mailer variables
  $to = get_option('admin_email');
  $subject = "Message from website.com";
  $headers = 'From: '. $email . "\r\n" .
    'Reply-To: ' . $email . "\r\n";

  if(!$human == 0){
    if($human != 2) my_contact_form_generate_response("error", $not_human); //not human!
    else {

      //validate email
      if(!filter_var($email, FILTER_VALIDATE_EMAIL))
        my_contact_form_generate_response("error", $email_invalid);
      else //email is valid
      {
        //validate presence of name and message
        if(empty($name) || empty($message)){
          my_contact_form_generate_response("error", $missing_content);
        }
        else //ready to go!
        {
          $sent = wp_mail($to, $subject, strip_tags($message), $headers);
          if($sent) my_contact_form_generate_response("success", $message_sent); //message sent!
          else my_contact_form_generate_response("error", $message_unsent); //message wasn't sent
        }
      }
    }
  }
  else if ($_POST['submitted']) my_contact_form_generate_response("error", $missing_content);
get_header(); ?>

<div class="breadcrumbs">
        <div class="container">
            <h1 class="pull-left"><a href="<?php echo get_page_link(); ?>"><?php the_title(); ?></a></h1>
        </div>
    </div>
<section class="content">
    	<div class="container">
        	<div class="row">
				<div class="col-xs-12 col-md-9">
					<div class="col-sm-12 col-md-12 col-xs-12">
					
					<?php echo $response; ?>
						<form action="<?php the_permalink(); ?>" method="post">
						
						<div class="row">
							<div class="form-group col-sm-12 col-md-6 col-xs-12">
                            <input class="form-control" type="text" name="message_name" value="<?php echo esc_attr($_POST['message_name']); ?>" placeholder="Name*">
                        </div>
                        </div>
                        
                        <div class="row">
							<div class="form-group col-sm-12 col-md-6 col-xs-12">
                            <input class="form-control" name="message_email" value="<?php echo esc_attr($_POST['message_email']); ?>" placeholder="Email*" type="email">
                        </div>
                        </div>

						<div class="row">
							<div class="form-group col-sm-12 col-md-8 col-xs-12">
                            <textarea class="form-control" placeholder="Message*" rows="6" name="message_text"><?php echo esc_textarea($_POST['message_text']); ?></textarea>
                        </div>
                        </div>

						<div class="row">
							<div class="form-group col-sm-12 col-md-2 col-xs-12">
                            <input class="form-control" name="message_human" type="text" placeholder="5-3=?">
                        </div>
                        </div>
						    <input type="hidden" name="submitted" value="1">
						<div class="row">
							<div class="form-group col-sm-12 col-md-6 col-xs-12">
						<button type="submit" class="btn btn-lg rounded pi-btn-red">Send</button>
                        </div>
                        </div>
						 </form>


					</div><!-- end col-sm-12 -->
                        
				</div><!-- end col-sm-9 -->	

<?php get_sidebar(); ?>
<?php get_footer(); ?>