How to check if a PHP session is empty?

To check if a PHP session is empty, you can use the empty() function. For example:

<?php

if (empty($_SESSION)) {
  // The session is empty
}

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Alternatively, you can check if the $_SESSION array is set and has a count of zero:

<?php

if (isset($_SESSION) && count($_SESSION) == 0) {
  // The session is empty
}

Note that the $_SESSION array is only available if a session has been started using the session_start() function.