为什么（$ _SESSION = [];）使服务器无法处理请求？

Question

I'm trying to clear the variables from a session and start a new one. From reading around about the variable issue, I think I discovered that this is the right answer:

( $_SESSION = [];)

But when I add that line to my code, on a line by itself within the PHP code, I get a message that "[the server] is currently unable to handle this request," indicating "HTTP ERROR 500."

Without that one command, the page works fine (except that the variables don't behave as I want them to). But every time I activate that line, I get the error. How can I clear the variables without making the server angry?

Update: I have also tried session_destroy(), but it has the same effect. Here is a little more context:

<?php 
session_destroy();

session_set_cookie_params(3600,"/");
session_start();
?>

If I comment out the session_destroy() line, the page loads with no trouble. But with that line, I get the error.

Final update for others with this question: I've marked the correct answer. I needed to start the new session before unsetting the variables from the last one.

Answer 1

You should not use session_destroy() before session_start(). Try this:

session_start(); session_set_cookie_params(3600,"/"); session_destroy();

Answer 2

To remove all session variables use:

session_unset(); 

if you are having issues after destroying your session, then it is likely that your code is trying to access session variables that have not been set. I like to check with isset() eg

$myVar = "";
if (isset($_SESSION('MyVar')) $MyVar = $_SESSION('MyVar');