wp-settings loads plugins before pluggable.php is included

[kingjeffrey]

When manually initializing WordPress (like in a page that handles AJAX requests) to access all WordPress functions, it is typical to begin the file with:

	define('WP_USE_THEMES', FALSE);
	require($_SERVER['DOCUMENT_ROOT'] . '/wp-blog-header.php');

However, if a plugin calls the get_userdata() function, the page will deliver this fatal error:

	Fatal error: Call to undefined function get_userdata() in [...]/wp-includes/user.php on line 1402

The "Maintenance" plugin is an example of one that causes this issue.

When the plugin is loaded in wp-settings.php line 198, it calls the get_userdata() function. But the get_userdata() function is not defined until wp-includes/pluggable.php is included on line 202 of wp-settings.

So this issue is not limited to calling get_userdata(), but any function defined in wp-includes/pluggable.php.

A simple fix to this, assuming wp-includes/pluggable.php does not depend on the plugins being loaded (which it very may well), is to swap the order of loading in wp-settings.php