Docs: Improve documentation for Custom_Image_Header and `Custom_Bac…

…kground` constructors.

Follow-up to [4673], [8656], [12890], [13041].

Props faisalahammad, cadic.
Fixes #58049.

git-svn-id: https://develop.svn.wordpress.org/trunk@57169 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/class-custom-background.php

@@ -42,8 +42,11 @@ class Custom_Background {
 	 * Constructor - Registers administration header callback.
 	 *
 	 * @since 3.0.0
-	 * @param callable $admin_header_callback
-	 * @param callable $admin_image_div_callback Optional custom image div output callback.
+	 *
+	 * @param callable $admin_header_callback    Optional. Administration header callback.
+	 *                                           Default empty string.
+	 * @param callable $admin_image_div_callback Optional. Custom image div output callback.
+	 *                                           Default empty string.
 	 */
 	public function __construct( $admin_header_callback = '', $admin_image_div_callback = '' ) {
 		$this->admin_header_callback    = $admin_header_callback;

src/wp-admin/includes/class-custom-image-header.php

@@ -47,11 +47,13 @@ class Custom_Image_Header {
 	private $updated;
 
 	/**
-	 * Constructor - Register administration header callback.
+	 * Constructor - Registers administration header callback.
 	 *
 	 * @since 2.1.0
-	 * @param callable $admin_header_callback
-	 * @param callable $admin_image_div_callback Optional custom image div output callback.
+	 *
+	 * @param callable $admin_header_callback    Administration header callback.
+	 * @param callable $admin_image_div_callback Optional. Custom image div output callback.
+	 *                                           Default empty string.
 	 */
 	public function __construct( $admin_header_callback, $admin_image_div_callback = '' ) {
 		$this->admin_header_callback    = $admin_header_callback;