Multisite Global $pagenow variable

[thorthecoder]

When the site is configured as multisite, plugins are loaded before "vars.php", causing plugin getting null value when trying to access the $pagenow variable.

Sample Plugin : Brightcove Video Connect
Defect : Setting page is empty
Caused by : In the setting page logic, it will check whether $pagenow is in the array of 'admin-ajax.php', 'admin.php', 'post-new.php', 'edit.php', 'post.php'. And since the $pagenow is not initialized yet, it will just display an empty page.

[jeremyfelt]

Hi @thorthecoder, welcome to Trac and thanks for opening a ticket.

This looks like an issue that should be solvable by making a small adjustment to the plugin. There's a related ​open issue on the GitHub repository now.

If the plugin requires $pagenow to determine what actions it should add (​existing code), then that area of code can change to run after plugins_loaded fires so that $pagenow is available to help with the decision.

Note that this should only be an issue when configured as a must use (mu) plugin rather than a network or site activated plugin within multisite.

[podpirate]

$pagenow not being available at mu-plugin inclusion has an additional consequence, which has not been mentioned yet.

function determine_locale() is checking for $GLOBALS['pagenow'] in line 141. As a result, a network activated plugin, which is using one of the WP l10n functions during startup will cause a PHP Notice undefined index… notice on the login popup window.

From a network administrator's point of view, I would not expect a big difference between a network-wide activated plugin and a plugin that I activated on every site in the network individually. (unless the plugin provides some network-specific funtionality)
EDIT: e.g. plugins that call wp_is_mobile() outside a hook will work well on single-site activation, but will cause a WSOD on network-activation.

Plugin authors (or at least a considerable majority of them), might expect the wp core to reliably provide an identical environment, in both cases network activation and single-site activation.