Is there anything special required to make a plugin work in a multisite environment?

Question

I've been developing plugins for about a year now, but not having any experience with multisite environments, whenever a question comes up that is specific to that environment I'm generally stumped.

Today, I got a question regarding Document Gallery. The question states that the user attempted to install the plugin as a network admin, but then could not see the plugin in the dash for the network admin or individual site. They additionally state that the shortcode does nothing.

There are thousands of people using the plugin without any issue so I'm confident it works as expected for non-multisite, but I just want to verify that there is nothing special about multisite that could make a plugin that otherwise works nonfunctional on multisite installs.

Answer 1

You can use the is_multisite() function to test to see if you're installed in a Multisite-enabled site. That way, if there is any functionality you need to provide specific to a Multisite installation, you can do it like this:

if( is_multisite() ) {
    // special code here
}

Most plugins that I've written at work, for our Multisite environment, don't have anything special defined for the Multisite environment.

Additionally...

I downloaded your Document Gallery plugin to a multisite installation I've got set up for a project I'm working on. When I Network Enabled the plugin -- ie, enabled it for every site in my multisite installation -- it remained visible in the Network Admin > Plugins section, but not in the individuals sites' Plugins sections.

When I Network Disabled it, it then reappeared in the individual sites' Plugins sections. I was then able to enable it for individual sites.

When I Network Enabled the plugin, the [dg] shortcode was available for use. When I enabled it on an individual site instead, the [dg] shortcode was available in that site.

This is the behaviour I've always seen from Multisite, which I've used at work since WP Version 3.0.

Your user might have encountered a plugin conflict. All I can report is that your plugin works as expected on my WordPress 3.5.1 Multisite installation.