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class-wp-walker.php (12730B)

---

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