理解PHP文件和AJAX调用

I'm slowly learning PHP ;-) I'm having difficulties understanding how separate PHP-files work together.

I make AJAX calls to different php files that all need to be connected to the backend (Parse). Such as:

sign_up.php
login.php
verify_email.php
get_something_out_of_the_database.php

What is the standard way to stay logged in over the different php files? (or what is the google search term for it..?)

Update: Thanks for all your answers about 'sessions'. I doesn't work very well yet, so i made a new question.

Thanks!

Remzo

You can do this for example by storing the login-data in a session-variable and checking it at the start of every new page.

Example: You check if login-data is valid. Then

session_start();
$_SESSION["login"] = $loginname;

At the start of another page:

session_start();
if(!isset($_SESSION["login"]) || $_SESSION["login"] != "check_somehow")
{
  header("Location: logout.php");
  exit;
}

For logging out you can use

session_start();
session_destroy();

On the start of your user logged in, you can do something like

session_start();
$_SESSION['USER'] = <some user info>;

In your other pages you can see if

if(isset($_SESSION['USER'])){
  // do something

}

at last on logout

session_destroy();

will kill the session

You should use PHP sessions. These are a way to store information on visitor browser between multiple pages...

To start a session, you first need to add session_start(); in every PHP file you intend to use it. Usually it's added in a header.php

Then, you can use sessions already.

To store a result:

$_SESSION['some_data'] = $var;

To retrieve a result in another page, for example:

echo $_SESSION['some_data']; // will echo $var