Execute A Function from Functions.php in Form - php

Question

I'm building a form which displays a certain piece of user_meta data and I want to be able to update this usermeta on form submit.
This is what I have at the moment;
function my_form_funnction() {
global $current_user;
$vat_no = get_user_meta( get_current_user_id(), 'vat_number', true );
?>
<form name="setPrices" action="" method="POST">
<label for="lowPrice">Vat Number: </label>
<input type="text" id="vat_number" name="vat_number" value="<?php echo $vat_no ?>" />
<button type="submit">Save</button>
</form>
<?php update_user_meta( get_current_user_id(), 'vat_number', esc_attr($_POST['vat_number']) );
}
But the thing is the php that updates the user meta does so when the page loads, I only want it to do it when the user pressess save.

Answer 1

You need to use Ajax to update information on a page without refreshing it. Try jQuery! It is a realy simple way to use Ajax. For example:
<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<button onclick="javascript:la()">Save or do smth</button>
<div id="a">Here will be included the loadable thing</div>
<script>
function la(){
$("#a").load("/functions.php?func=my_form_function");
}
</script>
And in functions.php you may set:
if(isset($_GET["func"]){
if($_GET["func"] == "my_form_function"){
my_form_funnction();
}
}