3 * A class for displaying various tree-like structures.
5 * Extend the Walker class to use it, see examples below. Child classes
6 * do not need to implement all of the abstract methods in the class. The child
7 * only needs to implement the methods that are needed.
16 * What the class handles.
34 * Max number of pages walked by the paged walker
40 protected $max_pages = 1;
43 * Whether the current element has children or not.
45 * To be used in start_el().
51 protected $has_children;
54 * Make private properties readable for backwards compatibility.
59 * @param string $name Property to get.
60 * @return mixed Property.
62 public function __get( $name ) {
67 * Make private properties settable for backwards compatibility.
72 * @param string $name Property to set.
73 * @param mixed $value Property value.
74 * @return mixed Newly-set property.
76 public function __set( $name, $value ) {
77 return $this->$name = $value;
81 * Make private properties checkable for backwards compatibility.
86 * @param string $name Property to check if set.
87 * @return bool Whether the property is set.
89 public function __isset( $name ) {
90 return isset( $this->$name );
94 * Make private properties un-settable for backwards compatibility.
99 * @param string $name Property to unset.
101 public function __unset( $name ) {
102 unset( $this->$name );
106 * Starts the list before the elements are added.
108 * The $args parameter holds additional values that may be used with the child
109 * class methods. This method is called at the start of the output list.
114 * @param string $output Passed by reference. Used to append additional content.
115 * @param int $depth Depth of the item.
116 * @param array $args An array of additional arguments.
118 public function start_lvl( &$output, $depth = 0, $args = array() ) {}
121 * Ends the list of after the elements are added.
123 * The $args parameter holds additional values that may be used with the child
124 * class methods. This method finishes the list at the end of output of the elements.
129 * @param string $output Passed by reference. Used to append additional content.
130 * @param int $depth Depth of the item.
131 * @param array $args An array of additional arguments.
133 public function end_lvl( &$output, $depth = 0, $args = array() ) {}
136 * Start the element output.
138 * The $args parameter holds additional values that may be used with the child
139 * class methods. Includes the element output also.
144 * @param string $output Passed by reference. Used to append additional content.
145 * @param object $object The data object.
146 * @param int $depth Depth of the item.
147 * @param array $args An array of additional arguments.
148 * @param int $current_object_id ID of the current item.
150 public function start_el( &$output, $object, $depth = 0, $args = array(), $current_object_id = 0 ) {}
153 * Ends the element output, if needed.
155 * The $args parameter holds additional values that may be used with the child class methods.
160 * @param string $output Passed by reference. Used to append additional content.
161 * @param object $object The data object.
162 * @param int $depth Depth of the item.
163 * @param array $args An array of additional arguments.
165 public function end_el( &$output, $object, $depth = 0, $args = array() ) {}
168 * Traverse elements to create list from elements.
170 * Display one element if the element doesn't have any children otherwise,
171 * display the element and its children. Will only traverse up to the max
172 * depth and no ignore elements under that depth. It is possible to set the
173 * max depth to include all depths, see walk() method.
175 * This method should not be called directly, use the walk() method instead.
179 * @param object $element Data object.
180 * @param array $children_elements List of elements to continue traversing.
181 * @param int $max_depth Max depth to traverse.
182 * @param int $depth Depth of current element.
183 * @param array $args An array of arguments.
184 * @param string $output Passed by reference. Used to append additional content.
185 * @return null Null on failure with no changes to parameters.
187 public function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output ) {
192 $id_field = $this->db_fields['id'];
193 $id = $element->$id_field;
195 //display this element
196 $this->has_children = ! empty( $children_elements[ $id ] );
197 if ( isset( $args[0] ) && is_array( $args[0] ) ) {
198 $args[0]['has_children'] = $this->has_children; // Backwards compatibility.
201 $cb_args = array_merge( array(&$output, $element, $depth), $args);
202 call_user_func_array(array($this, 'start_el'), $cb_args);
204 // descend only when the depth is right and there are childrens for this element
205 if ( ($max_depth == 0 || $max_depth > $depth+1 ) && isset( $children_elements[$id]) ) {
207 foreach( $children_elements[ $id ] as $child ){
209 if ( !isset($newlevel) ) {
211 //start the child delimiter
212 $cb_args = array_merge( array(&$output, $depth), $args);
213 call_user_func_array(array($this, 'start_lvl'), $cb_args);
215 $this->display_element( $child, $children_elements, $max_depth, $depth + 1, $args, $output );
217 unset( $children_elements[ $id ] );
220 if ( isset($newlevel) && $newlevel ){
221 //end the child delimiter
222 $cb_args = array_merge( array(&$output, $depth), $args);
223 call_user_func_array(array($this, 'end_lvl'), $cb_args);
227 $cb_args = array_merge( array(&$output, $element, $depth), $args);
228 call_user_func_array(array($this, 'end_el'), $cb_args);
232 * Display array of elements hierarchically.
234 * Does not assume any existing order of elements.
236 * $max_depth = -1 means flatly display every element.
237 * $max_depth = 0 means display all levels.
238 * $max_depth > 0 specifies the number of display levels.
242 * @param array $elements An array of elements.
243 * @param int $max_depth The maximum hierarchical depth.
244 * @return string The hierarchical item output.
246 public function walk( $elements, $max_depth) {
248 $args = array_slice(func_get_args(), 2);
251 if ($max_depth < -1) //invalid parameter
254 if (empty($elements)) //nothing to walk
257 $parent_field = $this->db_fields['parent'];
260 if ( -1 == $max_depth ) {
261 $empty_array = array();
262 foreach ( $elements as $e )
263 $this->display_element( $e, $empty_array, 1, 0, $args, $output );
268 * Need to display in hierarchical order.
269 * Separate elements into two buckets: top level and children elements.
270 * Children_elements is two dimensional array, eg.
271 * Children_elements[10][] contains all sub-elements whose parent is 10.
273 $top_level_elements = array();
274 $children_elements = array();
275 foreach ( $elements as $e) {
276 if ( 0 == $e->$parent_field )
277 $top_level_elements[] = $e;
279 $children_elements[ $e->$parent_field ][] = $e;
283 * When none of the elements is top level.
284 * Assume the first one must be root of the sub elements.
286 if ( empty($top_level_elements) ) {
288 $first = array_slice( $elements, 0, 1 );
291 $top_level_elements = array();
292 $children_elements = array();
293 foreach ( $elements as $e) {
294 if ( $root->$parent_field == $e->$parent_field )
295 $top_level_elements[] = $e;
297 $children_elements[ $e->$parent_field ][] = $e;
301 foreach ( $top_level_elements as $e )
302 $this->display_element( $e, $children_elements, $max_depth, 0, $args, $output );
305 * If we are displaying all levels, and remaining children_elements is not empty,
306 * then we got orphans, which should be displayed regardless.
308 if ( ( $max_depth == 0 ) && count( $children_elements ) > 0 ) {
309 $empty_array = array();
310 foreach ( $children_elements as $orphans )
311 foreach( $orphans as $op )
312 $this->display_element( $op, $empty_array, 1, 0, $args, $output );
319 * paged_walk() - produce a page of nested elements
321 * Given an array of hierarchical elements, the maximum depth, a specific page number,
322 * and number of elements per page, this function first determines all top level root elements
323 * belonging to that page, then lists them and all of their children in hierarchical order.
325 * $max_depth = 0 means display all levels.
326 * $max_depth > 0 specifies the number of display levels.
330 * @param int $max_depth The maximum hierarchical depth.
331 * @param int $page_num The specific page number, beginning with 1.
332 * @return string XHTML of the specified page of elements
334 public function paged_walk( $elements, $max_depth, $page_num, $per_page ) {
337 if ( empty($elements) || $max_depth < -1 )
340 $args = array_slice( func_get_args(), 4 );
343 $parent_field = $this->db_fields['parent'];
346 if ( -1 == $max_depth )
347 $total_top = count( $elements );
348 if ( $page_num < 1 || $per_page < 0 ) {
352 if ( -1 == $max_depth )
354 $this->max_pages = 1;
357 $start = ( (int)$page_num - 1 ) * (int)$per_page;
358 $end = $start + $per_page;
359 if ( -1 == $max_depth )
360 $this->max_pages = ceil($total_top / $per_page);
364 if ( -1 == $max_depth ) {
365 if ( !empty($args[0]['reverse_top_level']) ) {
366 $elements = array_reverse( $elements );
368 $start = $total_top - $end;
369 $end = $total_top - $oldstart;
372 $empty_array = array();
373 foreach ( $elements as $e ) {
375 if ( $count < $start )
377 if ( $count >= $end )
379 $this->display_element( $e, $empty_array, 1, 0, $args, $output );
385 * Separate elements into two buckets: top level and children elements.
386 * Children_elements is two dimensional array, e.g.
387 * $children_elements[10][] contains all sub-elements whose parent is 10.
389 $top_level_elements = array();
390 $children_elements = array();
391 foreach ( $elements as $e) {
392 if ( 0 == $e->$parent_field )
393 $top_level_elements[] = $e;
395 $children_elements[ $e->$parent_field ][] = $e;
398 $total_top = count( $top_level_elements );
400 $this->max_pages = ceil($total_top / $per_page);
404 if ( !empty($args[0]['reverse_top_level']) ) {
405 $top_level_elements = array_reverse( $top_level_elements );
407 $start = $total_top - $end;
408 $end = $total_top - $oldstart;
410 if ( !empty($args[0]['reverse_children']) ) {
411 foreach ( $children_elements as $parent => $children )
412 $children_elements[$parent] = array_reverse( $children );
415 foreach ( $top_level_elements as $e ) {
418 // For the last page, need to unset earlier children in order to keep track of orphans.
419 if ( $end >= $total_top && $count < $start )
420 $this->unset_children( $e, $children_elements );
422 if ( $count < $start )
425 if ( $count >= $end )
428 $this->display_element( $e, $children_elements, $max_depth, 0, $args, $output );
431 if ( $end >= $total_top && count( $children_elements ) > 0 ) {
432 $empty_array = array();
433 foreach ( $children_elements as $orphans )
434 foreach( $orphans as $op )
435 $this->display_element( $op, $empty_array, 1, 0, $args, $output );
441 public function get_number_of_root_elements( $elements ){
444 $parent_field = $this->db_fields['parent'];
446 foreach ( $elements as $e) {
447 if ( 0 == $e->$parent_field )
453 // Unset all the children for a given top level element.
454 public function unset_children( $e, &$children_elements ){
456 if ( !$e || !$children_elements )
459 $id_field = $this->db_fields['id'];
462 if ( !empty($children_elements[$id]) && is_array($children_elements[$id]) )
463 foreach ( (array) $children_elements[$id] as $child )
464 $this->unset_children( $child, $children_elements );
466 if ( isset($children_elements[$id]) )
467 unset( $children_elements[$id] );