Normally when you install a distribution of Linux server software (Apache with a PHP module enabled) there will be a signature in the headers sent to the browser. You can remove those headers quite easily so nobody know what exact versions of software your are using, which is a far more secure solution for your Apache server:

In your php.ini search for expose_php and set it to 'Off' e.g:

expose_php = Off

In your Apache configuration search for 'ServerTokens' (in my case it is located in): /etc/apache2/conf.d/security

Set to one of: Full | OS | Minor | Minimal | Major | Prod, where Full conveys the most information, and Prod the least. Prod only says 'Apache' in the headers sent about 'Server', not version etc. Therefore use:

ServerTokens Prod