Avoid scrolling up on submit form php - php

Question

I am working on a simple contact form.
It uses PHP code to show a "Thank you" message after the submit.
The problem there is about it scrolls up as soon as you submit the form.
PHP CODE:
<?php
session_name("fancyform");
session_start();
$_SESSION['n1'] = rand(1,20);
$_SESSION['n2'] = rand(1,20);
$_SESSION['expect'] = $_SESSION['n1']+$_SESSION['n2'];
if(isset($_SESSION['sent']))
{
$success='<h1>Thank you!</h1>';
unset($_SESSION['sent']);
}
?>
FORM CODE (SECTION):
<section id="revealAnim" class="page5">
<div class="page_container">
<div class="icono red"></div>
<p class="titulo_cabecera">Necesito soluciones!</p>
<p class="subtitulo_cabecera">Rellena el formulario y estaremos en contacto en menos de 24h</p>
<form class="demo-form" name ="demo-form" data-parsley-validate method="post" action="submit.php" >
<ul>
<li class="js-hide-label">
<label for="name">Nombre:</label>
<input type="text" placeholder="Nombre" id="name" name="name" data-parsley-trigger="change" required tabindex="1" autocomplete="off" value="<?php echo (isset($_SESSION['post']['name']) ? $_SESSION['post']['name'] : ''); ?>" >
</li>
<li class="js-hide-label">
<label for="email">Your Email:</label>
<input type="email" placeholder="Your Email" id="email" data-parsley-trigger="change" name="email" autocomplete="off" required tabindex="2" value="<?php echo (isset($_SESSION['post']['email']) ? $_SESSION['post']['email'] : ''); ?>">
</li>
<li class="js-hide-label">
<label for="message">Message:</label>
<textarea placeholder="Message…" id="message" name="message" tabindex="3" required data-parsley-trigger="keyup" textarea id="message" data-parsley-minlength="20" data-parsley-maxlength="100" data-parsley-minlength-message = "Come on! You need to enter at least a 20 caracters long comment.." data-parsley-validation-threshold="10"><?php echo (isset($_SESSION['post']['message']) ? $_SESSION['post']['message'] : ''); ?></textarea>
</li>
<input class="btn btn-default"type="submit" name="button" id="button" value="Submit" />
</ul>
<?php echo isset($success)?$success:''; ?>
</form>
</section>
Should I work on a Javascript form to avoid the problem? Or there is any solution working on the PHP code?.
Otherwise I am working with ONE PAGE SCROLL so the scrolls breaks my usability on the 90% of users, since they have to scroll back to the bottom page (they are 5) to see if the form has been submited.
Thank you

Answer 1

You could either use AJAX/Javascript like you have suggested, or you could redirect the visitor to an id tag.
http://example.com/index.php#contact
So the body will automatically be scrolled to the contact form after submit.

Answer 2

By default a web page reloads when a form is submitted. This is how PHP works.
When a user clicks on the submit button an http request is sent to the server and thus requesting new data, so the page must be reloaded to preview response data.
The way to avoid this is by using AJAX
there is a good example found on this link: Submit A Form Without Page Refresh using jQuery