$ _session ['error']在php中意味着什么

Question

I have this php code

if (isset($_SESSION['error']))
{
echo "<span id='error'><p>" . $_SESSION['error'] . "</p></span>";
unset($_SESSION['error']);
}

What Does $_SESSION['error'] means and unset one please explain

Answer 1

$_SESSION contains all session variables (user ID of logged in user for example). You can set a session variable like this:

$_SESSION['foo'] = 'bar';

And access it later (after multiple page loads still, that's why it's so useful) using:

$foo = $_SESSION['foo'];
echo $foo; //Displays 'bar'

Your code checks if there is a session variable set, and if so display an error and unset the session variable. So I would guess this is to show a one-time error when something went wrong. Using a session variable means you can execute this code on a different page then where the error happened.