Can't get debug information with WP_DEBUG

I am trying to do some debugging of my WordPress site, and turned on WP_DEBUG to do so. I can’t get it to produce any output at all, either on screen or in an error log.

Progress so far:

In wp-config.php I have:

define(‘WP_DEBUG’, true);
define(‘WP_DEBUG_LOG’, true);

I have placed a logging message in a function that I know is being called (because I’ve also been messing with the _output_ of that function, and all my changes are reflected on screen)

error_log(‘EEK’,0);

The error_log message doesn’t appear on screen. The debug.log file was not created. So I created a debug.log file manually, in wp-content, with +rwx permission for everyone, and fiddled with the selinux context, which is now reported as

unconfined_u:object_r:httpd_sys_content_t:s0

No error messages are being added to the debug.log file, and nothing appears on screen.

As it happens (this may end up being the key), I _also_ have a problem on this installation that it won’t upload any media, giving the message ‘The uploaded file could not be moved to wp-content/uploads/2015/11’. I haven’t been bothering about it, since it’s just a test install and the live version works ok. But they feel like probably the same underlying issue.

(My upload dir also has chmod 777 all over the place, and as free a set of SELinux constraints as I can figure out – doesn’t seem to help.)

thanks!