<?php
/**
* Post API: Walker_PageDropdown class
*
* @package WordPress
* @subpackage Post
* @since 4.4.0
*/

/**
* Core class used to create an HTML drop-down list of pages.
*
* @since 2.1.0
*
* @see Walker
*/
class Walker_PageDropdown extends Walker {

/**
* What the class handles.
*
* @since 2.1.0
* @var string
*
* @see Walker::$tree_type
*/
public $tree_type = 'page';

/**
* Database fields to use.
*
* @since 2.1.0
* @var string[]
*
* @see Walker::$db_fields
* @todo Decouple this
*/
public $db_fields = array(
'parent' => 'post_parent',
'id' => 'ID',
);

/**
* Starts the element output.
*
* @since 2.1.0
* @since 5.9.0 Renamed `$page` to `$data_object` and `$id` to `$current_object_id`
* to match parent class for PHP 8 named parameter support.
*
* @see Walker::start_el()
*
* @param string $output Used to append additional content. Passed by reference.
* @param WP_Post $data_object Page data object.
* @param int $depth Optional. Depth of page in reference to parent pages.
* Used for padding. Default 0.
* @param array $args Optional. Uses 'selected' argument for selected page to
* set selected HTML attribute for option element. Uses
* 'value_field' argument to fill "value" attribute.
* See wp_dropdown_pages(). Default empty array.
* @param int $current_object_id Optional. ID of the current page. Default 0.
*/
public function start_el( &$output, $data_object, $depth = 0, $args = array(), $current_object_id = 0 ) {
// Restores the more descriptive, specific name for use within this method.
$page = $data_object;

$pad = str_repeat( '&nbsp;', $depth * 3 );

if ( ! isset( $args['value_field'] ) || ! isset( $page->{$args['value_field']} ) ) {
$args['value_field'] = 'ID';
}

$output .= "\t<option class=\"level-$depth\" value=\"" . esc_attr( $page->{$args['value_field']} ) . '"';
if ( $page->ID === (int) $args['selected'] ) {
$output .= ' selected="selected"';
}
$output .= '>';

$title = $page->post_title;
if ( '' === $title ) {
/* translators: %d: ID of a post. */
$title = sprintf( __( '#%d (no title)' ), $page->ID );
}

/**
* Filters the page title when creating an HTML drop-down list of pages.
*
* @since 3.1.0
*
* @param string $title Page title.
* @param WP_Post $page Page data object.
*/
$title = apply_filters( 'list_pages', $title, $page );

$output .= $pad . esc_html( $title );
$output .= "</option>\n";
}
}