I was able to install Zabbix 2.5 trunk, but I noticed that login.php wasn't being interpreted. I looked at /var/log/httpd/error_log and was received this in the log file when i attempted to load the page:

[Tue Aug 04 15:56:17 2015] [error] [client 10.90.16.120] PHP Parse error: syntax error, unexpected '[' in /var/www/html/index.php on line 29

I was never told that I should be using php5.4 or greater.

Maybe put some exception handling in there?

The page worked fine once I upgraded to php 5.4. (Centos 6.x uses php 5.3, so this could be a big deal to support if you don't handle the error)