refactor: upgrade to PHP 7.4

src/includes/class-core.php

@@ -54,7 +54,7 @@ class Core {
 	 *
 	 * @var Loader $loader Maintains and registers all hooks for the plugin.
 	 */
-	protected $loader;
+	protected ?\footnotes\includes\Loader $loader = null;
 
 	/**
 	 * The unique identifier of this plugin
@@ -63,7 +63,7 @@ class Core {
 	 *
 	 * @var string $plugin_name The string used to uniquely identify this plugin.
 	 */
-	protected $plugin_name;
+	protected string $plugin_name;
 
 	/**
 	 * The current version of the plugin.
@@ -73,7 +73,7 @@ class Core {
 	 *
 	 * @var string $version The current version of the plugin.
 	 */
-	protected $version;
+	protected string $version;
 
 	/**
 	 * Builds the core of the plugin.

src/includes/class-loader.php

@@ -31,7 +31,7 @@ class Loader {
 	 *
 	 * @var  (string|int|object)[][]  $actions  The actions registered with WordPress to fire when the plugin loads.
 	 */
-	protected $actions;
+	protected array $actions;
 
 	/**
 	 * The array of filters registered with WordPress.
@@ -41,7 +41,7 @@ class Loader {
 	 *
 	 * @var  (string|int|object)[][]  $filters  The filters registered with WordPress to fire when the plugin loads.
 	 */
-	protected $filters;
+	protected array $filters;
 
 	/**
 	 * Initialize the collections used to maintain the actions and filters.

src/includes/class-settings.php

@@ -1106,15 +1106,13 @@ class Settings {
 	/**********************************************************************
 	 *      SETTINGS STORAGE.
 	 **********************************************************************/
-
 	/**
 	 * Stores a singleton reference of this class.
 	 *
-	 * @var  Settings
 	 *
 	 * @since  1.5.0
 	 */
-	private static $a_obj_instance;
+	private static ?\footnotes\includes\Settings $a_obj_instance = null;
 
 	/**
 	 * Contains all Settings Container names.

src/includes/class-template.php

@@ -51,28 +51,22 @@ class Template {
 	 * Contains the content of the template after initialize.
 	 *
 	 * @since  1.5.0
-	 *
-	 * @var string
 	 */
-	private $a_str_original_content = '';
+	private ?string $a_str_original_content = '';
 
 	/**
 	 * Contains the content of the template after initialize with replaced place holders.
 	 *
 	 * @since  1.5.0
-	 *
-	 * @var string
 	 */
-	private $a_str_replaced_content = '';
+	private string $a_str_replaced_content = '';
 
 	/**
 	 * Plugin Directory
 	 *
 	 * @since  2.4.0d3
-	 *
-	 * @var  string
 	 */
-	public $plugin_directory;
+	public string $plugin_directory;
 
 	/**
 	 * Class Constructor. Reads and loads the template file without replace any placeholder.