PHP Fatal Error Failed opening required File

If you have SELinux running, you might have to grant httpd permission to read from /home dir using:

 sudo setsebool httpd_read_user_content=1

It's not actually an Apache related question. Nor even a PHP related one. To understand this error you have to distinguish a path on the virtual server from a path in the filesystem.

require operator works with files. But a path like this

                          /common/configs/config_templates.inc.php

only exists on the virtual HTTP server, while there is no such path in the filesystem. The correct filesystem path would be

/home/viapics1/public_html/common/configs/config_templates.inc.php

where

/home/viapics1/public_html

part is called the Document root and it connects the virtual world with the real one. Luckily, web-servers usually have the document root in a configuration variable that they share with PHP. So if you change your code to something like this

require_once $_SERVER['DOCUMENT_ROOT'].'/common/configs/config_templates.inc.php';

it will work from any file placed in any directory!

Update: eventually I wrote an article that explains the difference between relative and absolute paths, in the file system and on the web server, which explains the matter in detail, and contains some practical solutions. Like, such a handy variable doesn't exist when you run your script from a command line. In this case a technique called "a single entry point" is to the rescue. You may refer to the article above for the details as well.