How do I share a PHP variable between multiple pages?

Question

The idea/goal:

I have a username and password inside a text file on my computer. The form on the index page allows the user to sign in with their us

Answer 1

Use $_SESSION -!

session_start();
$_SESSION['username'] = $_POST['username'];

You of course want to filter/sanitize/validate your $_POST data, but that is outside of the scope of this question...

As long as you call session_start(); before you use $_SESSION - the values in the $_SESSION array will persist across pages until the user closes the browser.

If you want to end the session before that, like in a logout button --- use session_destroy()