Apache detection not always accurate

[raamdev]

As of v160417, Comet Cache is not properly setting the $is_apache and $is_nginx globals, which means the routines that rely on checking the values of those globals are not behaving as expected.

As Jason mentions below, those globals are set by WordPress, so the fact that we have a report indicating that Apache-only routines ran when Nginx was being used indicates that there must be a failure occurring with the detection.

For example, if WordPress incorrectly reports that the web server is Apache, then Comet Cache will attempt to add or remove from the .htaccess file, which in certain scenarios results in site owners who are running Nginx seeing an annoying message about Comet Cache being unable to add/remove from the .htaccess file (which isn't even applicable in their case).

Failed to update your /.htaccess file automatically. Most likely a permissions error. Please make sure it has permissions 644 or higher (perhaps 666). Once you've done this, please try saving the Comet Cache options again.

While we have a utility to check if the web server is Apache or Nginx, we're not actually using those utilities at the moment.

We might also be able to improve the Dashboard messages that are web-server specific. For example, we might add a link to the message that says "Not using Apache?" that dismisses the notice and sets an option key so as to prevent Apache-related errors from appearing.

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Originally reported in this private ticket: https://websharks.zendesk.com/agent/tickets/12292

[jaswrks]

While we have a utility to check if the web server is Apache or Nginx, we're not actually using those utilities to set the $is_apache and $is_nginx globals.

Just wanted to mention that we shouldn't set those globals in the CC plugin. Those are WordPress core globals. See: https://github.com/WordPress/WordPress/blob/703d5bdc8deb17781e9c6d8f0dd7e2c6b6353885/wp-includes/vars.php#L100

I can't be sure until I look closer, but those isApache(), isNginx() methods may have been introduced by me at some point in order to make it possible for us to run those checks in the early phase of WordPress; i.e., before the globals are available maybe.

[raamdev]

@jaswsinc Thanks. I didn't realize those were set by WordPress. I've updated my original issue above to clarify the problem and I've removed the high priority label, as it sounds like this is not as widespread as I thought it might be.