What determines whether firefox will open a file (PHP or HTML) in the browser

Using Ubuntu 18.04

SAME PAGE PROCESSING
Quote:

How can you process a form on the same page vs using a separate process page.

I got this code, copied here from the internet, as an example of having a form and php open on same page.

I am trying to open it as: test2.php. It does not work. A window comes up asking if you should open the file with firefox.When you say yes the samw window asks the saqme question. Over and Over and Over.



Code:<?php
//Form submitted
if(isset($_POST['submit'])) {
//Error checking
if(!$_POST['yourname']) {
$error['yourname'] = "<p>Please supply your name.</p>\n";
}
if(!$_POST['address']) {
$error['address'] = "<p>Please supply your address.</p>\n";
}

//No errors, process
if(!is_array($error)) {
//Process your form

//Display confirmation page
echo "<p>Thank you for your submission.</p>\n";

//Require or include any page footer you might have
//here as well so the style of your page isn't broken.
//Then exit the script.
exit;
}
}
?>

<form method="post" action="<?=$_SERVER['PHP_SELF']?>">
<?=$error['yourname']?>
<p><label for="yourname">Your Name:</label><input type="text" id="yourname" name="yourname" value="<?=($_POST['yourname'] ? htmlentities($_POST['yourname']) : '')?>" /></p>
<?=$error['address']?>
<p><label for="address">Your Address:</label><input type="text" id="address" name="address" value="<?=($_POST['address'] ? htmlentities($_POST['address']) : '')?>" /></p>
<p><input type="submit" name="submit" value="Submit" /></p>
</form>