Why are the Apache headers stripped from my web application?

Question

Why are the Apache headers removed from my request when testing my web application? 

Answer

This will occur when the CGI PHP handlers are in use. For most use cases, you should utilize the suPHP, LSAPI, or PHP-FPM PHP handlers. PHP-FPM still strips some headers such as "content-length" for security reasons.

By default, cPanel systems are issued with mod_ruid2 and PHP-FPM. These packages are compatible and enable htaccess header manipulation.

How to enable PHP-FPM for a domain

mod_ruid2 is not compatible with LSAPI, suPHP, or mod_suexec, and must be removed before these other options can be installed. We recommend having either mod_ruid2 or mod_suexec installed at all times.

What's the importance of running scripts as the user?

To utilize LSAPI or suPHP, you should remove mod_ruid2, substitute mod_suexec, and additionally install mod_lsapi or mod_suphp:

How to install an Apache module in WHM