451 lines
13 KiB
PHP
451 lines
13 KiB
PHP
<?php
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/**
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* A class for displaying various tree-like structures.
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*
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* Extend the Walker class to use it, see examples below. Child classes
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* do not need to implement all of the abstract methods in the class. The child
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* only needs to implement the methods that are needed.
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*
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* @since 2.1.0
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*
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* @package WordPress
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* @abstract
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*/
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#[AllowDynamicProperties]
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class Walker {
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/**
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* What the class handles.
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*
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* @since 2.1.0
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* @var string
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*/
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public $tree_type;
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/**
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* DB fields to use.
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*
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* @since 2.1.0
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* @var string[]
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*/
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public $db_fields;
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/**
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* Max number of pages walked by the paged walker.
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*
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* @since 2.7.0
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* @var int
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*/
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public $max_pages = 1;
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/**
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* Whether the current element has children or not.
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*
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* To be used in start_el().
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*
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* @since 4.0.0
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* @var bool
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*/
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public $has_children;
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/**
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* Starts the list before the elements are added.
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*
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* The $args parameter holds additional values that may be used with the child
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* class methods. This method is called at the start of the output list.
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*
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* @since 2.1.0
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* @abstract
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*
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* @param string $output Used to append additional content (passed by reference).
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* @param int $depth Depth of the item.
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* @param array $args An array of additional arguments.
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*/
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public function start_lvl( &$output, $depth = 0, $args = array() ) {}
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/**
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* Ends the list of after the elements are added.
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*
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* The $args parameter holds additional values that may be used with the child
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* class methods. This method finishes the list at the end of output of the elements.
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*
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* @since 2.1.0
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* @abstract
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*
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* @param string $output Used to append additional content (passed by reference).
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* @param int $depth Depth of the item.
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* @param array $args An array of additional arguments.
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*/
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public function end_lvl( &$output, $depth = 0, $args = array() ) {}
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/**
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* Starts the element output.
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*
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* The $args parameter holds additional values that may be used with the child
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* class methods. Also includes the element output.
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*
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* @since 2.1.0
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* @since 5.9.0 Renamed `$object` (a PHP reserved keyword) to `$data_object` for PHP 8 named parameter support.
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* @abstract
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*
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* @param string $output Used to append additional content (passed by reference).
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* @param object $data_object The data object.
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* @param int $depth Depth of the item.
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* @param array $args An array of additional arguments.
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* @param int $current_object_id Optional. ID of the current item. Default 0.
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*/
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public function start_el( &$output, $data_object, $depth = 0, $args = array(), $current_object_id = 0 ) {}
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/**
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* Ends the element output, if needed.
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*
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* The $args parameter holds additional values that may be used with the child class methods.
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*
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* @since 2.1.0
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* @since 5.9.0 Renamed `$object` (a PHP reserved keyword) to `$data_object` for PHP 8 named parameter support.
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* @abstract
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*
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* @param string $output Used to append additional content (passed by reference).
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* @param object $data_object The data object.
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* @param int $depth Depth of the item.
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* @param array $args An array of additional arguments.
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*/
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public function end_el( &$output, $data_object, $depth = 0, $args = array() ) {}
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/**
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* Traverses elements to create list from elements.
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*
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* Display one element if the element doesn't have any children otherwise,
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* display the element and its children. Will only traverse up to the max
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* depth and no ignore elements under that depth. It is possible to set the
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* max depth to include all depths, see walk() method.
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*
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* This method should not be called directly, use the walk() method instead.
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*
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* @since 2.5.0
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*
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* @param object $element Data object.
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* @param array $children_elements List of elements to continue traversing (passed by reference).
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* @param int $max_depth Max depth to traverse.
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* @param int $depth Depth of current element.
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* @param array $args An array of arguments.
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* @param string $output Used to append additional content (passed by reference).
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*/
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public function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output ) {
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if ( ! $element ) {
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return;
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}
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$id_field = $this->db_fields['id'];
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$id = $element->$id_field;
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// Display this element.
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$this->has_children = ! empty( $children_elements[ $id ] );
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if ( isset( $args[0] ) && is_array( $args[0] ) ) {
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$args[0]['has_children'] = $this->has_children; // Back-compat.
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}
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$this->start_el( $output, $element, $depth, ...array_values( $args ) );
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// Descend only when the depth is right and there are children for this element.
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if ( ( 0 == $max_depth || $max_depth > $depth + 1 ) && isset( $children_elements[ $id ] ) ) {
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foreach ( $children_elements[ $id ] as $child ) {
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if ( ! isset( $newlevel ) ) {
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$newlevel = true;
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// Start the child delimiter.
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$this->start_lvl( $output, $depth, ...array_values( $args ) );
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}
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$this->display_element( $child, $children_elements, $max_depth, $depth + 1, $args, $output );
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}
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unset( $children_elements[ $id ] );
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}
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if ( isset( $newlevel ) && $newlevel ) {
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// End the child delimiter.
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$this->end_lvl( $output, $depth, ...array_values( $args ) );
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}
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// End this element.
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$this->end_el( $output, $element, $depth, ...array_values( $args ) );
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}
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/**
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* Displays array of elements hierarchically.
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*
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* Does not assume any existing order of elements.
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*
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* $max_depth = -1 means flatly display every element.
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* $max_depth = 0 means display all levels.
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* $max_depth > 0 specifies the number of display levels.
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*
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* @since 2.1.0
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* @since 5.3.0 Formalized the existing `...$args` parameter by adding it
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* to the function signature.
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*
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* @param array $elements An array of elements.
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* @param int $max_depth The maximum hierarchical depth.
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* @param mixed ...$args Optional additional arguments.
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* @return string The hierarchical item output.
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*/
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public function walk( $elements, $max_depth, ...$args ) {
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$output = '';
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// Invalid parameter or nothing to walk.
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if ( $max_depth < -1 || empty( $elements ) ) {
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return $output;
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}
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$parent_field = $this->db_fields['parent'];
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// Flat display.
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if ( -1 == $max_depth ) {
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$empty_array = array();
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foreach ( $elements as $e ) {
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$this->display_element( $e, $empty_array, 1, 0, $args, $output );
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}
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return $output;
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}
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/*
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* Need to display in hierarchical order.
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* Separate elements into two buckets: top level and children elements.
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* Children_elements is two dimensional array. Example:
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* Children_elements[10][] contains all sub-elements whose parent is 10.
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*/
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$top_level_elements = array();
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$children_elements = array();
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foreach ( $elements as $e ) {
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if ( empty( $e->$parent_field ) ) {
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$top_level_elements[] = $e;
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} else {
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$children_elements[ $e->$parent_field ][] = $e;
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}
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}
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/*
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* When none of the elements is top level.
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* Assume the first one must be root of the sub elements.
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*/
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if ( empty( $top_level_elements ) ) {
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$first = array_slice( $elements, 0, 1 );
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$root = $first[0];
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$top_level_elements = array();
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$children_elements = array();
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foreach ( $elements as $e ) {
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if ( $root->$parent_field == $e->$parent_field ) {
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$top_level_elements[] = $e;
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} else {
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$children_elements[ $e->$parent_field ][] = $e;
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}
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}
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}
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foreach ( $top_level_elements as $e ) {
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$this->display_element( $e, $children_elements, $max_depth, 0, $args, $output );
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}
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/*
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* If we are displaying all levels, and remaining children_elements is not empty,
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* then we got orphans, which should be displayed regardless.
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*/
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if ( ( 0 == $max_depth ) && count( $children_elements ) > 0 ) {
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$empty_array = array();
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foreach ( $children_elements as $orphans ) {
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foreach ( $orphans as $op ) {
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$this->display_element( $op, $empty_array, 1, 0, $args, $output );
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}
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}
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}
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return $output;
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}
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/**
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* Produces a page of nested elements.
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*
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* Given an array of hierarchical elements, the maximum depth, a specific page number,
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* and number of elements per page, this function first determines all top level root elements
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* belonging to that page, then lists them and all of their children in hierarchical order.
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*
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* $max_depth = 0 means display all levels.
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* $max_depth > 0 specifies the number of display levels.
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*
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* @since 2.7.0
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* @since 5.3.0 Formalized the existing `...$args` parameter by adding it
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* to the function signature.
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*
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* @param array $elements An array of elements.
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* @param int $max_depth The maximum hierarchical depth.
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* @param int $page_num The specific page number, beginning with 1.
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* @param int $per_page Number of elements per page.
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* @param mixed ...$args Optional additional arguments.
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* @return string XHTML of the specified page of elements.
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*/
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public function paged_walk( $elements, $max_depth, $page_num, $per_page, ...$args ) {
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if ( empty( $elements ) || $max_depth < -1 ) {
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return '';
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}
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$output = '';
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$parent_field = $this->db_fields['parent'];
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$count = -1;
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if ( -1 == $max_depth ) {
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$total_top = count( $elements );
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}
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if ( $page_num < 1 || $per_page < 0 ) {
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// No paging.
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$paging = false;
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$start = 0;
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if ( -1 == $max_depth ) {
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$end = $total_top;
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}
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$this->max_pages = 1;
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} else {
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$paging = true;
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$start = ( (int) $page_num - 1 ) * (int) $per_page;
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$end = $start + $per_page;
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if ( -1 == $max_depth ) {
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$this->max_pages = ceil( $total_top / $per_page );
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}
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}
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// Flat display.
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if ( -1 == $max_depth ) {
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if ( ! empty( $args[0]['reverse_top_level'] ) ) {
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$elements = array_reverse( $elements );
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$oldstart = $start;
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$start = $total_top - $end;
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$end = $total_top - $oldstart;
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}
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$empty_array = array();
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foreach ( $elements as $e ) {
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$count++;
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if ( $count < $start ) {
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continue;
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}
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if ( $count >= $end ) {
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break;
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}
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$this->display_element( $e, $empty_array, 1, 0, $args, $output );
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}
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return $output;
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}
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/*
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* Separate elements into two buckets: top level and children elements.
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* Children_elements is two dimensional array, e.g.
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* $children_elements[10][] contains all sub-elements whose parent is 10.
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*/
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$top_level_elements = array();
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$children_elements = array();
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foreach ( $elements as $e ) {
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if ( empty( $e->$parent_field ) ) {
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$top_level_elements[] = $e;
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} else {
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$children_elements[ $e->$parent_field ][] = $e;
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}
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}
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$total_top = count( $top_level_elements );
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if ( $paging ) {
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$this->max_pages = ceil( $total_top / $per_page );
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} else {
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$end = $total_top;
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}
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if ( ! empty( $args[0]['reverse_top_level'] ) ) {
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$top_level_elements = array_reverse( $top_level_elements );
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$oldstart = $start;
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$start = $total_top - $end;
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$end = $total_top - $oldstart;
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}
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if ( ! empty( $args[0]['reverse_children'] ) ) {
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foreach ( $children_elements as $parent => $children ) {
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$children_elements[ $parent ] = array_reverse( $children );
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}
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}
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foreach ( $top_level_elements as $e ) {
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$count++;
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// For the last page, need to unset earlier children in order to keep track of orphans.
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if ( $end >= $total_top && $count < $start ) {
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$this->unset_children( $e, $children_elements );
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}
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if ( $count < $start ) {
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continue;
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}
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if ( $count >= $end ) {
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break;
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}
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$this->display_element( $e, $children_elements, $max_depth, 0, $args, $output );
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}
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if ( $end >= $total_top && count( $children_elements ) > 0 ) {
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$empty_array = array();
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foreach ( $children_elements as $orphans ) {
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foreach ( $orphans as $op ) {
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$this->display_element( $op, $empty_array, 1, 0, $args, $output );
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}
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}
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}
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return $output;
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}
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/**
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* Calculates the total number of root elements.
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*
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* @since 2.7.0
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*
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* @param array $elements Elements to list.
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* @return int Number of root elements.
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*/
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public function get_number_of_root_elements( $elements ) {
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$num = 0;
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$parent_field = $this->db_fields['parent'];
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foreach ( $elements as $e ) {
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if ( empty( $e->$parent_field ) ) {
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$num++;
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}
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}
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return $num;
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}
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/**
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* Unsets all the children for a given top level element.
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*
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* @since 2.7.0
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*
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* @param object $element The top level element.
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* @param array $children_elements The children elements.
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*/
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public function unset_children( $element, &$children_elements ) {
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if ( ! $element || ! $children_elements ) {
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return;
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}
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$id_field = $this->db_fields['id'];
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$id = $element->$id_field;
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if ( ! empty( $children_elements[ $id ] ) && is_array( $children_elements[ $id ] ) ) {
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foreach ( (array) $children_elements[ $id ] as $child ) {
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$this->unset_children( $child, $children_elements );
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}
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}
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unset( $children_elements[ $id ] );
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}
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}
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