/** * 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 * @access public * @var string */ public $tree_type; /** * DB fields to use. * * @since 2.1.0 * @access protected * @var array */ protected $db_fields; /** * Max number of pages walked by the paged walker * * @since 2.7.0 * @access protected * @var int */ protected $max_pages = 1; /** * Whether the current element has children or not. * * To be used in start_el(). * * @since 4.0.0 * @access protected * @var bool */ protected $has_children; /** * Make private properties readable for backwards compatibility. * * @since 4.0.0 * @access public * * @param string $name Property to get. * @return mixed Property. */ public function __get( $name ) { return $this->$name; } /** * Make private properties settable for backwards compatibility. * * @since 4.0.0 * @access public * * @param string $name Property to set. * @param mixed $value Property value. * @return mixed Newly-set property. */ public function __set( $name, $value ) { return $this->$name = $value; } /** * Make private properties checkable for backwards compatibility. * * @since 4.0.0 * @access public * * @param string $name Property to check if set. * @return bool Whether the property is set. */ public function __isset( $name ) { return isset( $this->$name ); } /** * Make private properties un-settable for backwards compatibility. * * @since 4.0.0 * @access public * * @param string $name Property to unset. */ public function __unset( $name ) { unset( $this->$name ); } /** * 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 Passed by reference. Used to append additional content. * @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 Passed by reference. Used to append additional content. * @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 Passed by reference. Used to append additional content. * @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 Passed by reference. Used to append additional content. * @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. * @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 Passed by reference. Used to append additional content. * @return null Null on failure with no changes to parameters. */ 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; // Backwards compatibility. } $cb_args = array_merge( array(&$output, $element, $depth), $args); call_user_func_array(array($this, 'start_el'), $cb_args); // descend only when the depth is right and there are childrens for this element if ( ($max_depth == 0 || $max_depth > $depth+1 ) && isset( $children_elements[$id]) ) { foreach( $children_elements[ $id ] as $child ){ if ( !isset($newlevel) ) { $newlevel = true; //start the child delimiter $cb_args = array_merge( array(&$output, $depth), $args); call_user_func_array(array($this, 'start_lvl'), $cb_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 $cb_args = array_merge( array(&$output, $depth), $args); call_user_func_array(array($this, 'end_lvl'), $cb_args); } //end this element $cb_args = array_merge( array(&$output, $element, $depth), $args); call_user_func_array(array($this, 'end_el'), $cb_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 * * @param array $elements An array of elements. * @param int $max_depth The maximum hierarchical depth. * @return string The hierarchical item output. */ public function walk( $elements, $max_depth) { $args = array_slice(func_get_args(), 2); $output = ''; if ($max_depth < -1) //invalid parameter return $output; if (empty($elements)) //nothing to walk 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 ( 0 == $e->$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 ( ( $max_depth == 0 ) && 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 * * @param int $max_depth The maximum hierarchical depth. * @param int $page_num The specific page number, beginning with 1. * @return string XHTML of the specified page of elements */ public function paged_walk( $elements, $max_depth, $page_num, $per_page ) { /* sanity check */ if ( empty($elements) || $max_depth < -1 ) return ''; $args = array_slice( func_get_args(), 4 ); $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 ( 0 == $e->$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; } public function get_number_of_root_elements( $elements ){ $num = 0; $parent_field = $this->db_fields['parent']; foreach ( $elements as $e) { if ( 0 == $e->$parent_field ) $num++; } return $num; } // Unset all the children for a given top level element. 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, $children_elements ); if ( isset($children_elements[$id]) ) unset( $children_elements[$id] ); } } // Walker