WordPress/wp-includes/class-wp-walker.php

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<?php
/**
* A class for displaying various tree-like structures.
*
* Extend the Walker class to use it, see examples at the 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. Also, the methods are
* not strictly abstract in that the parameter definition needs to be followed.
* The child classes can have additional parameters.
*
* @package WordPress
* @since 2.1.0
* @abstract
*/
class Walker {
/**
* What the class handles.
*
* @since 2.1.0
* @var string
* @access public
*/
var $tree_type;
/**
* DB fields to use.
*
* @since 2.1.0
* @var array
* @access protected
*/
var $db_fields;
/**
* Max number of pages walked by the paged walker
*
* @since 2.7.0
* @var int
* @access protected
*/
var $max_pages = 1;
/**
* Starts the list before the elements are added.
*
* Additional parameters are used in child classes. 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 $output Passed by reference. Used to append additional content.
*/
function start_lvl( &$output, $depth = 0, $args = array() ) {}
/**
* Ends the list of after the elements are added.
*
* Additional parameters are used in child classes. 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 $output Passed by reference. Used to append additional content.
*/
function end_lvl( &$output, $depth = 0, $args = array() ) {}
/**
* Start the element output.
*
* Additional parameters are used in child classes. 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 $output Passed by reference. Used to append additional content.
*/
function start_el( &$output, $object, $depth, $args, $current_object_id = 0 ) {}
/**
* Ends the element output, if needed.
*
* Additional parameters are used in child classes. The args parameter holds
* additional values that may be used with the child class methods.
*
* @since 2.1.0
* @abstract
*
* @param string $output Passed by reference. Used to append additional content.
*/
function end_el( &$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 shouldn't 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
* @param string $output Passed by reference. Used to append additional content.
* @return null Null on failure with no changes to parameters.
*/
function display_element( $element, &$children_elements, $max_depth, $depth=0, $args, &$output ) {
if ( !$element )
return;
$id_field = $this->db_fields['id'];
//display this element
if ( isset( $args[0] ) && is_array( $args[0] ) )
$args[0]['has_children'] = ! empty( $children_elements[$element->$id_field] );
$cb_args = array_merge( array(&$output, $element, $depth), $args);
call_user_func_array(array($this, 'start_el'), $cb_args);
$id = $element->$id_field;
// 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.
*
* It is a generic function which 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
* @param int $max_depth
* @return string
*/
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;
$id_field = $this->db_fields['id'];
$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.
*
* @package WordPress
* @since 2.7
* @param int $max_depth = 0 means display all levels; $max_depth > 0 specifies the number of display levels.
* @param int $page_num the specific page number, beginning with 1.
* @return XHTML of the specified page of elements
*/
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 = '';
$id_field = $this->db_fields['id'];
$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, 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;
}
$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;
}
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
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] );
}
}