Description:
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PHP SESSION variable $_SESSION['user_level'] is not saved after the page is redirected using header(location: ...). Session_write_close()is used right before redirect. After redirect die() is called. After a second attempt at login, everything works!

Reproduce code:
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<?php
// If login successfully ->

// Change session properties
$_SESSION['user_level'] = 7;
// Force session to save changes before redirection
session_write_close(); // REQUIRED
// Regenerate session id for security + fix bug in which some session variables are lost during redirect
session_regenerate_id(true);
// Redirect to Access main page
header('Location: http://www.domain.com/access/main.php');
die();

?>

Expected result:
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At the new page (the one the user was redirected to) the $SESSION['user_level'] should == 7. However, the session variable was not saved, as the user is redirected back to the login page. After a second attempt at logging in, everything works as expected.

Actual result:
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Redirected back to login page, because when php checked if the user had the proper credentials

if ($_SESSION['user_level'] != 7) {
 // redirect back to login page
}

Other improtant information: session_start(); is called on every page.