Question
Why do my (php-) scripts have issues accessing files in /tmp?
Answer
With the migration to systemd in UCS 4.3.0 a feature implemented by systemd (private tmp) apache uses a different kind of model to store temporary files.
Option 1
This feature can be disabled in systemd by creating a drop-in extension to the apache2.service unit and changing the corresponding setting. Create the file /etc/systemd/system/apache2.service.d/override.conf with the following content:
[Service]
PrivateTmp=false
Reload systemd and restart Apache afterwards:
systemctl daemon-reload
systemctl restart apache2
Option 2
Edit your scripts to take care of this change. Examples can be found here.