Completely isolate a plugin view so it doesn’t load the theme

Preferably don’t load the plugin URL directly (well, unless it is a public URL and you can pass whatever data you need as querystrings) as this makes it difficult to load WordPress and access any stored data (as the path is not always determinable), but instead either:

1. load the view via a querystring and check for it in WordPress load OR
2. similar, but add it to an AJAX action querystring function.

Option 1. via /any-page/?my-action=trigger

add_action('init', 'my_plugin_view');
function my_plugin_view() {
    // check for querystring trigger
    if (!isset($_REQUEST['my-action']) || ($_REQUEST['my-action'] != 'trigger-value')) {return;}

    if (!is_user_logged_in()) {
       wp_die('You need to be logged in to do this.');
    } else {
        // ... plugin view output code ...
    }
    exit;
}

Option 2. via /wp-admin/admin-ajax.php?action=my_plugin_view

// logged in users
add_action('wp_ajax_my_plugin_view', 'my_plugin_view');

function my_plugin_view() {
    // ... plugin view output code ...
    exit;
}

// logged out users (optional) 
add_action('wp_ajax_nopriv_my_plugin_view', 'my_plugin_view');
function my_plugin_logged_out_message() {
    wp_die('You need to be logged in to do this.');
}

As you can see there is a difference in the target URL that is used as well as how logged out users are handled (if needed, in this example it is assumed the user must be logged in, but this distinction is not necessary for compltely public view.)

Either are viable options, but probably the AJAX method is the more common “WordPress way” of doing this. Of course any plugin scripts and styles would need to be added directly to the output instead of enqueueing them as normal.

Codex Reference: AJAX in Plugins