Step 3: Create our admin page

In our class’ constructor, let’s register three new actions which are required to add an admin page on WordPress:

• addAdminMenu will add a new page in the WordPress left menu. There will be also a callback to another method containing the page’s content.
• storeAdminData will be called whenever the user clicks the “Save settings” button.
• Addadminscripts will register a new Javascript file to our Wordpress Admin in order to save the form’s data.