PHP how to check if session already exists

To check whether a session already exists or started in PHP, you can use the isset() or session_status() function.

The session_status() function will return PHP_SESSION_ACTIVE when you have sessions enabled and one exists.

You can use this function inside an if block to check your session as follows:

<?php
// 👇 enable PHP session
session_start();

// 👇 check if session exists. returns true
if (session_status() == PHP_SESSION_ACTIVE) {
    print "session already exists";
}

When you have called the session_start() function, then a session has been created by PHP.

Besides using session_status(), you can also use the isset() function and check the $_SESSION superglobal like this:

if (isset($_SESSION)) {
    print "session exists";
}

Using the isset() function also allows you to check if a specific key exists in the $_SESSION array as shown below:

// 👇 check if userid key exists in $_SESSION
if (isset($_SESSION['userid'])) {
    print "session exists";
}

Depending on your situation, you can choose to use the session_status() or isset() function to check if a session exists in PHP.