Does is_admin() really provide a plugin performance improvement?

Question

I have this block in my Main.php class which loads the admin, core and front classes that make up my plugin

function registerObjects() {
    // register the front
    $controller = new front\Controller( $this->get_plugin_name(), $this->get_version());
    $controller->registerHooks($this->loader);

    // register the BHAA objects with support actions and filters.
    $adminController = new admin\AdminController($this->get_plugin_name(), $this->get_version());
    $adminController->registerHooks($this->loader);
    $runnerAdminController = new admin\RunnerAdminController();
    $runnerAdminController->registerHooks($this->loader);
    $raceAdminController = new admin\RaceAdminController();
    $raceAdminController->registerHooks($this->loader);
    $leagueAdminController = new admin\LeagueAdminController();
    $leagueAdminController->registerHooks($this->loader);
    $registrarAdminController = new admin\RegistrarAdminController();
    $registrarAdminController->registerHooks($this->loader);

    // register the core objects
    $raceCpt = new core\cpt\RaceCPT();
    $raceCpt->registerHooks($this->loader);
    $houseCpt = new core\cpt\HouseCPT();
    $houseCpt->registerHooks($this->loader);
    $leagueCpt = new core\cpt\LeagueCPT();
    $leagueCpt->registerHooks($this->loader);
    $connections = new core\Connections();
    $connections->registerHooks($this->loader);
    $eventExpresso = new core\eventexpresso\EventExpresso();
    $eventExpresso->registerHooks($this->loader);

    new core\standard\StandardShortcode();
    new core\race\RaceShortcode();
    new core\league\LeagueShortcode();
    new core\runner\RunnerShortcode();
    $resultsShortcode = new core\results\ResultsShortcode();
    $resultsShortcode->registerHooks($this->loader);
}

I can use the is_admin() function to restrict loading of the admin controller classes like this

function registerObjects() {
    // register the front
    $controller = new front\Controller( $this->get_plugin_name(), $this->get_version());
    $controller->registerHooks($this->loader);

    // register the BHAA objects with support actions and filters.
    if(is_admin()) {
        $adminController = new admin\AdminController($this->get_plugin_name(), $this->get_version());
        $adminController->registerHooks($this->loader);
        $runnerAdminController = new admin\RunnerAdminController();
        $runnerAdminController->registerHooks($this->loader);
        $raceAdminController = new admin\RaceAdminController();
        $raceAdminController->registerHooks($this->loader);
        $leagueAdminController = new admin\LeagueAdminController();
        $leagueAdminController->registerHooks($this->loader);
        $registrarAdminController = new admin\RegistrarAdminController();
        $registrarAdminController->registerHooks($this->loader);
    }

    // register the core objects
    $raceCpt = new core\cpt\RaceCPT();
    $raceCpt->registerHooks($this->loader);
    $houseCpt = new core\cpt\HouseCPT();
    $houseCpt->registerHooks($this->loader);
    $leagueCpt = new core\cpt\LeagueCPT();
    $leagueCpt->registerHooks($this->loader);
    $connections = new core\Connections();
    $connections->registerHooks($this->loader);
    $eventExpresso = new core\eventexpresso\EventExpresso();
    $eventExpresso->registerHooks($this->loader);

    new core\standard\StandardShortcode();
    new core\race\RaceShortcode();
    new core\league\LeagueShortcode();
    new core\runner\RunnerShortcode();
    $resultsShortcode = new core\results\ResultsShortcode();
    $resultsShortcode->registerHooks($this->loader);
}

Since the actions and filter that my classes register are already specific to the public or admin area's of the wordpress site - what value is the is_admin() function really adding here? As i see using the method avoid registering some hook methods, which wouldn't get called anyway.

I have a number of CPT classes which are used on the public and admin site. Are there any best practice guidelines for using is_admin() here?

Answer 1

The is_admin() function is basically used to check whether the running request is routing on /wp-admin/. Calling the is_admin() conditional function, you can restrict files you only want to load when a request goes through the /wp-admin/.

Note that is_admin() and is_super_admin() are not the same and both handle different conditions.

Looking forward, when sending an ajax request, it goes through the /wp-admin/ folder, so it would be nice to do:

if ( is_admin() || wp_doing_ajax() ) {
    // code here
}

Talking about best usage, I would say optimization, efficiency, and speed. Loading the entire class files at once by doing if ( is_admin() ) { ... } is never a good practice. You should also extend the check to an independent action that requires a condition. For example:

if ( is_admin() ) {
     require_once '/path/to/file/';
    if ( $_GET['type'] ?? false ) {
        include_once '/path/to/another/file/';
    }
}