PHP Can't Open PHPMyAdmin Library

PHP can't open common.inc.php; worked yesterday.

[webfoo]

Hello All! It has been a few years but I am back! Not sure if this is the right forum for this thread, mods please redirect me if I'm wrong.

I'm having an issue today with a PHPMyAdmin installation that has been running without issue for several months. I went to PMA this morning to do a bulk data upload, and I got a white screen instead of the login screen. Yesterday this was not the case - everything worked. The website itself works fine, and queries the database properly, so I know PHP and MySQL are both running.

The PHP error log shows this message:

[03-Aug-2016 08:43:40 America/New_York] PHP Fatal error: require_once(): Failed opening required './libraries/common.inc.php' (include_path='.;C:\php\pear') in C:\inetpub\wwwroot\phpMyAdmin\js\whitelist.php on line 21

I checked, and the common.inc.php file IS present. Any ideas?

EDIT: I should point out that I am running PHP 5.6 on IIS / Windows Server 2012 R2. PHPMyAdmin is version 4.5.4.1A.

[whitespace]

Presumably you are unaware of anything having changed since yesterday when "everything worked"?

Have permissions changed to make that file unreadable by the PHP process?

I wonder where it is trying to look for that file? It looks for that file relative to the CWD and a few lines above that (in "whitelist.php") it changes the CWD by moving up to the parent directory (which all seems a bit "risky" to me) - at least in the version of "whitelist.php" that I'm looking at (https://github.com/phpmyadmin/phpmyadmin/blob/master/js/whitelist.php).

Before line#21 in "whitelist.php" you could try checking what it thinks is the CWD or what the relative path resolves to:

throw new Exception(realpath('./libraries/common.inc.php'));

Assuming there isn't an exception handler that catches this exception you should get a fatal error with the absolute filesystem path of where it is looking.

[webfoo]

@Whitespace, you are correct - I am not aware of any changes made since yesterday (permissions or otherwise).

Oddly enough, PMA started working just fine again. Very peculiar! I am left to wonder what caused it to stop working, what caused it to start working again, and whether I will face this problem again in the future.

Thanks for your help.