A WordPress site we have been working on for a client suddenly started throwing a 500 error in wp-admin after we moved the site. We can access /wp-login.php and login, but as soon as we do, it throws the 500 error. The admin bar DOES show up across the front end of the site (which I have no problem viewing), but as expected, any of the links that go into wp-admin go to the 500 error.
Strangely, when I try to navigate to some of the css files inside /wp-admin/ like /wp-admin/css/common.css, it gives a 404. I have tried a few files and they all give 404 errors.
I have tried disabling all plugins and deleting the plugins folder to no avail. I have turned on error logging and the following is in it from today's visits:
[05-Aug-2016 17:54:08 UTC] PHP Warning: session_start(): open(/tmp/sess_8401a984d7d274c65ba969e6f67e30a2, O_RDWR) failed: Permission denied (13) in /home/garagedoor/public_html/wp-content/plugins/booked/booked.php on line 207
[05-Aug-2016 17:54:09 UTC] PHP Warning: Unknown: open(/tmp/sess_8401a984d7d274c65ba969e6f67e30a2, O_RDWR) failed: Permission denied (13) in Unknown on line 0
[05-Aug-2016 17:54:09 UTC] PHP Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in Unknown on line 0
[05-Aug-2016 17:54:09 UTC] PHP Warning: session_start(): open(/tmp/sess_8401a984d7d274c65ba969e6f67e30a2, O_RDWR) failed: Permission denied (13) in /home/garagedoor/public_html/wp-content/plugins/booked/booked.php on line 207
[05-Aug-2016 17:54:10 UTC] PHP Warning: Unknown: open(/tmp/sess_8401a984d7d274c65ba969e6f67e30a2, O_RDWR) failed: Permission denied (13) in Unknown on line 0
[05-Aug-2016 17:54:10 UTC] PHP Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in Unknown on line 0
[05-Aug-2016 17:56:07 UTC] PHP Warning: session_start(): open(/tmp/sess_8401a984d7d274c65ba969e6f67e30a2, O_RDWR) failed: Permission denied (13) in /home/garagedoor/public_html/wp-content/plugins/booked/booked.php on line 207
[05-Aug-2016 17:56:07 UTC] PHP Warning: Unknown: open(/tmp/sess_8401a984d7d274c65ba969e6f67e30a2, O_RDWR) failed: Permission denied (13) in Unknown on line 0
[05-Aug-2016 17:56:07 UTC] PHP Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in Unknown on line 0
After reading through the log I tried turning off all plugins again and the errors here stop, although the wp-admin is still unavailable.
I tried changing the permissions for the tmp folder in wp-config and in the server root to 777 temporarily and still no dice.
Lastly, I have tried moving the site to a local WAMP server environment on my computer and it works PERFECTLY after importing the database and changing the values in wp-config.php.
Does anyone have any advice on where to go from here? I am assuming it is a server issue but I wouldn't know where to look. Any advice is appreciated.
EDIT: I enabled error reporting through wordpress as well and got the following to output on the site:
Warning: session_start(): open(/tmp/sess_8401a984d7d274c65ba969e6f67e30a2, O_RDWR) failed: Permission denied (13) in /home/garagedoor/public_html/wp-content/plugins/booked/booked.php on line 207
Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/garagedoor/public_html/wp-includes/functions.php:3718) in /home/garagedoor/public_html/wp-content/plugins/booked/booked.php on line 207
Again, the booked plugin can be turned on and off (actually, all the plugins can be turned off) and I am still unable to access wp-admin. I am thinking it's a session error or maybe permissions error? How would I go about checking which it is?
I've tried setting the tmp directory to 777 but it's still not working.
/tmp/
matches the WP install, not just the directory permissions.