How should a module change the value of the global $user, execute its own code, and restore the original value of $user without causing the current user to be logged out if an error happens?

  • There is an old issue open about this, which adds a function that can properly handle this, even when called multiple times. See drupal.org/node/287292. Please review and test the patch there.
    – Berdir
    Apr 11 '11 at 1:24
  • 1
    There has been a Community Documentation create that has the solution to impersonate another user for Drupal 6, Drupal 7 and Drupal 8 on drupal.org: Safely Impersonating Another User.
    – iStryker
    Dec 22 '14 at 14:19

The drupal_cron_run() function gives a perfect example for exactly this, since it changes the current user to anonymous whenever cron is run, then switches back after it is done.

// Prevent session information from being saved while doing funky stuff.
$original_session_state = drupal_save_session();

// Force the current user to anonymous to ensure consistent permissions on
// funky stuff runs.
$original_user = $GLOBALS['user'];
$GLOBALS['user'] = drupal_anonymous_user(); // Or use user_load() for a non-anonymous user.

// Do funky stuff here...

// Restore the user.
$GLOBALS['user'] = $original_user;
  • Worth noting you can put the current user object away somewhere (in $GLOBALS or just in another variable for safe-keeping) and switch to any user by loading them in with user_load(). Which allows you to do some horrible things like masquerade as a specific users set up with specific permissions to perform a specific process. The principle is the same.
    – Greg
    Mar 4 '11 at 9:42
  • Only potential 1 problem with this piece of code. You should save the old session in a variable $old_session. Set the save session to false, then at the end drupal_save_session($old_session).
    – iStryker
    Dec 22 '14 at 14:21
  • Just a note for Drupal 8/9 You can use the AccountSwitcher service Jan 5 '21 at 1:25

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