Improve documentation for postbox_classes() and the postbox_classes_{$page}_{$id} hook within it

[DrewAPicture]

As pointed out on the Code Reference by @simonrcodrington, documentation for the $page and $id values in the postbox_classes_{$page}_{$id} hook is not quite correct.

$page actually represents the screen ID and $id represents the metabox ID. We should also improve the DocBlock for the postbox_classes() parent function by adding missing parameter descriptions.

<?php
/**
 * Filters the postbox classes for a specific screen and screen ID combo.
 *
 * The dynamic portions of the hook name, `$page` and `$id`, refer to
 * the screen and screen ID, respectively.
 *
 * @since 3.2.0
 *
 * @param string[] $classes An array of postbox classes.
 */
$classes = apply_filters( "postbox_classes_{$page}_{$id}", $classes );

[sharifkiberu]

@DrewAPicture Updated documentation in patch

[DrewAPicture]

Assigning the ticket to mark the good-first-bug as "claimed".

Hi @sharifkiberu, thanks for the patch! I think we still need adjustments to the postbox_classes() adding missing parameter descriptions and that should do it.

Trunk development is still ​closed pending the 5.0 release, but we should be able to get this in with 5.1.

[SergeyBiryukov]

In 45083:

Docs: Improve documentation for postbox_classes().

Rename $page and $id variables to $screen_id and $box_id for clarity.

Props sharifkiberu, DrewAPicture.
Fixes #45179.