I have the following array. It has a parent id that correspond with the id. I manage to create a function to sort and turn this array into a tree array. My problem stands that sometimes it does not work properly if the parent is after the child.
So how would I turn an array like the one below to a tree that doesn't need to be sorted first?
[0] => Array
(
[menu] =>
[parent] => 0
[id] => 1
)
,
[1] => Array
(
[menu] =>
[parent] =>
[id] => 2
)
,
[2] => Array
(
[menu] =>
[parent] => 1
[id] => 3
)
,
[3] => Array
(
[menu] =>
[parent] => 1
[id] => 4
)
,
[4] => Array
(
[menu] =>
[parent] => 4
[id] => 5
)
I have this function which does not work properly:
function page_tree($rows) {
if(!is_array($rows) || empty($rows) ){
return false;
}
// $rows = array(); //stores all the database rows that are to be converted into a tree
$tree = array(); //stores the tree
$tree_index = array(); //an array used to quickly find nodes in the tree
$id_column = "id"; //The column that contains the id of each node
$parent_column = "parent"; //The column that contains the id of each node's parent
$text_column = "title"; //The column to display when printing the tree to html
//build the tree - this will complete in a single pass if no parents are defined after children
// vp(count($rows) );die();
// while(count($rows) > 0){
foreach($rows as $row_id => $row){
$row_id = $row['id'];
if($row[$parent_column]){
if((!array_key_exists($row[$parent_column], $rows)) and (!array_key_exists($row[$parent_column], $tree_index))){
unset($rows[$row_id]);
}
else{
if(array_key_exists($row[$parent_column], $tree_index)){
$parent = & $tree_index[$row[$parent_column]];
$parent['children'][$row_id] =$row;
$parent['children'][$row_id]["children"] = array();
$tree_index[$row_id] = & $parent['children'][$row_id];
unset($rows[$row_id]);
}
}
}
else{
$tree[$row_id] = $row;
$tree[$row_id]["children"] = array();
$tree_index[$row_id] = & $tree[$row_id];
unset($rows[$row_id]);
}
}
// }
return $tree;
}
Please note: where parent is (empty) (='';) it means it's the root.
The trick is to keep a kind of index (named $all
below) with references to all nodes in the tree. The example below will add nodes that still need to be processed to an array named $dangling
and add the final output to the $output
array.
<?
// Test input
$input = array(
array( 'menu' => 'A', 'parent' => 2, 'id' => 4),
array( 'menu' => 'B', 'parent' => 1, 'id' => 3),
array( 'menu' => 'C', 'parent' => 2, 'id' => 1),
array( 'menu' => 'D', 'parent' => '', 'id' => 2)
);
$output = array();
$all = array();
$dangling = array();
// Initialize arrays
foreach ($input as $entry) {
$entry['children'] = array();
$id = $entry['id'];
// If this is a top-level node, add it to the output immediately
if ($entry['parent'] == '') {
$all[$id] = $entry;
$output[] =& $all[$id];
// If this isn't a top-level node, we have to process it later
} else {
$dangling[$id] = $entry;
}
}
// Process all 'dangling' nodes
while (count($dangling) > 0) {
foreach($dangling as $entry) {
$id = $entry['id'];
$pid = $entry['parent'];
// If the parent has already been added to the output, it's
// safe to add this node too
if (isset($all[$pid])) {
$all[$id] = $entry;
$all[$pid]['children'][] =& $all[$id];
unset($dangling[$entry['id']]);
}
}
}
print_r($output);
Note that this will go horribly wrong if your input data is incorrect (eg an item with an invalid value for parent will cause an infinite loop).
我发现包https://github.com/BlueM/Tree非常适合处理这种树结构。
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