refactor: upgrade to PHP 8.0

src/includes/class-convert.php

@@ -177,7 +177,7 @@ class Convert {
 	 * @todo  Review.
 	 * @todo  Single return type.
 	 */
-	public static function get_arrow( int $p_int_index = -1 ) {
+	public static function get_arrow( int $p_int_index = -1 ): string|array {
 		// Define all possible arrows.
 		$l_arr_arrows = array( '↑', '↥', '↟', '↩', '↲', '↵', '⇑', '⇡', '⇧', '￪' );
 		// Convert index to an integer.

src/includes/class-settings.php

@@ -1344,7 +1344,6 @@ class Settings {
 	/**
 	 * Returns a singleton of this class.
 	 *
-	 * @return  Settings
 	 *
 	 * @since  1.5.0
 	 * @todo  Remove?
@@ -1432,7 +1431,6 @@ class Settings {
 	 *
 	 * @param  int   $p_int_index  Index of the Setting Container.
 	 * @param  array $p_arr_new_values  The new Settings value(s).
-	 * @return  bool
 	 *
 	 * @since  1.5.0
 	 */

src/includes/class-template.php

@@ -180,7 +180,7 @@ class Template {
 	 * @param  string $p_str_extension  The file extension of the template.
 	 * @return  string|bool  `false` or the template path
 	 */
-	public function get_template( string $p_str_file_type, string $p_str_file_name, string $p_str_extension = 'html' ) {
+	public function get_template( string $p_str_file_type, string $p_str_file_name, string $p_str_extension = 'html' ): string|bool {
 		$located = false;
 
 		/*