Linux with Apache 2.4
After installing Zend Server on Linux with Apache 2.4, PHP doesn't load with an error:
httpd: Syntax error on line 353 of /etc/httpd/conf/httpd.conf: Syntax error on line 3 of /etc/httpd/conf.d/zendserver_php.conf: Cannot load /usr/local/zend/lib/apache2/libphp5.so into server: /usr/local/zend/lib/apache2/libphp5.so: undefined symbol: unixd_config
When using a single repo point for multiple Linux versions, you might install PHP built for Apache 2.2 on Apache 2.4 environment, or vice versa.
The PHP loading error above appears when installing PHP from the non-Apache 2.4 repo on Apache 2.4.
In General, Zend repos have multiple points, or symlinks, to collect packages around specific tasks, in this case, Apache 2.2 and 2.4 different builds.
Using Linux Installer:
Zend Server installer, which can be downloaded from Zend Server product page, is capable of automatically identifying the correct repo and install compatible PHP for your supported Linux platform.
Mirroring Zend Repos:
When you mirror a Zend repo point for your DEB / RPM install, keep details or directory name matching the Zend repo URL, which will help later in determining if the correct repo is to be used with a fresh installation.
The Linux installer uses Zend repos as reference. If you happen to mirror Zend repos within your organization storage, you can manually edit the repo file used by the Linux installer to match your mirrored repo, and still use the Linux installer instead of manual install.
These instructions can help you migrate to a working setup of Zend Server, or if you are provisioning a new system, skip the 3 steps to remove and just modify your repo and install a fresh server instance.