{$page_hook}

Used to call the registered callback for a plugin screen. This hook uses a dynamic hook name, `$page_hook`, which refers to a mixture of plugin page information including: 1. The page type. If the plugin page is registered as a submenu page, such as for Settings, the page type would be 'settings'. Otherwise the type is 'toplevel'. 2. A separator of '_page_'. 3. The plugin basename minus the file extension. Together, the three parts form the `$page_hook`. Citing the example above, the hook name used would be 'settings_page_pluginbasename'.