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<?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
* @access public
* @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 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.
*/
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 = '';
//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 ( ( $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 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
* @return string XHTML of the specified page of elements
*/
public function paged_walk( $elements, $max_depth, $page_num, $per_page ) {
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;
}
/**
* Calculates the total number of root elements.
*
* @since 2.7.0
* @access public
*
* @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 ( 0 == $e->$parent_field )
$num++;
}
return $num;
}
/**
* Unset all the children for a given top level element.
*
* @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 ] );
}
} // Walker