Build array recursively in CodeIgniter - php

Question

In CodeIgniter I'm trying to create a function. Need create array who will delete rows in db like:
$selected_items_by_id = array('1','2','3','4',); // --<<<Need Create This
$this->db->where_in('id', $selected_items_by_id);
$this->db->delete('mytable');
mytabe DB Structure of:
ID | NAME | PARENT_ID
1 Item1 0 // First Root item
2 Item2 1 // First Root sub item
3 Item3 2 // First Root sub sub item
4 Item4 3 // First Root sub sub sub item
5 Item5 0 // Second Root item
Items layout:
Item1
+Item2
++Item3
+++Item4
Item5
Here I'm getting the needed item id (from select box):
$id = $this->input->post('delete_menu_item');
Logic:
If item parent_id == 0, then item is root.
If Item is root item, in array will be only root item id
In array need $id and all $id subs (if they exist)
UPDATE
I try to make recursive function outside from CI.
Search function - to separate the necessary subaray:
function search($array, $key, $value)
{
$results = array();
if (is_array($array))
{
if (isset($array[$key]) && $array[$key] == $value)
$results[] = $array;
foreach ($array as $subarray)
$results = array_merge($results, search($subarray, $key, $value));
}
return $results;
}
I'm using this array, based on DB entries:
$array = array(
array('id' => '1', 'name' => 'Item1', 'parent_id' => '0'),
array('id' => '2', 'name' => 'Item2', 'parent_id' => '1'),
array('id' => '3', 'name' => 'Item3', 'parent_id' => '2'),
array('id' => '4', 'name' => 'Item4', 'parent_id' => '3'),
array('id' => '5', 'name' => 'Item5', 'parent_id' => '0'),
);
Recursive function:
function build_array($array,$id, $final = NULL){
$data = search($array, 'id', $id);
foreach ($data as $item):
if ($item['parent_id'] == 0){
$final[] = $item['id'];
}
else {
$parent_id = $item['parent_id'];
$final[] = $item['id'];
$final[] = $parent_id;
build_array($array, $parent_id, $final);
// Here go recursive
}
endforeach;
return $final;
}
$result = build_array($array,1);
var_dump($result);
What should be the function recursively?

Answer 1

If I understand what you are asking, you'll need to handle each item iteratively (in a loop).
So first you get an item, then you see if it has a parent - if so, get it's parent and start again, etc. This is one of the few cases where recursive functions can really come in handy.
You just build your final arrays as you go, until you run out of items - being aware that if you aren't careful you will get an infinite loop as you pull the same items over and over again.
Without more information on what you have to input and what you want to get as output, this is about as helpful as anyone can be. For more help you'll need to clarify what you want as output, code you've tried so far and what it's doing that you don't want, etc.

Answer 2

Ok. I will use the sample array you put together, only slightly different: Since ids are unique, there's no reason why they shouldn't serve as keys. Like so:
$array = array(
'1'=>array('name' => 'Item1', 'parent_id' => '0'),
'2'=>array('name' => 'Item2', 'parent_id' => '1'),
'3'=>array('name' => 'Item3', 'parent_id' => '2'),
'4'=>array('name' => 'Item4', 'parent_id' => '3'),
'5'=>array('name' => 'Item5', 'parent_id' => '0'),
);
Add the following methods to your controller/model/lib/whatever:
function children_of($arr,$id)
{
$r=array();
foreach($arr as $key=>$entry)
if($entry['parent_id']==$id) $r[]=$key;
return $r;
}
function subtree_array($arr,$id)
{
if(isset($arr[$id]))
{
$r=array($id);
foreach($this->children_of($arr,$id) as $child)
$r=array_merge($r,$this->subtree_array($arr,$child));
return $r;
}
else
return array(0); // (0) comes handy in SQL IN operations
}
children_of() returns the immediate children of $id in $arr.
subtree_array() returns an array including $id and all of its descendants in $arr. If $id is not a key of $arr, it returns array(0). That's because you say you want to use it in an SQL query, and a where clause like where xyz in () would be bogus, while where xyz in (0) wouldn't, and also would always return false since no item has a zero id (it seems to be reserved to denote root nodes).
So, the usage might be something like:
$id=$this->input->post('delete_menu_item');
$selected_items_by_id=subtree_array($aray,$id);

Answer 3

I tried to approach the task from the other side.
Using cascade delete, and everything is going sql side:
CREATE TABLE `navigation` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`name` VARCHAR(50) NOT NULL COLLATE 'utf8_general_ci',
`url` VARCHAR(50) NOT NULL COLLATE 'utf8_unicode_ci',
`position` MEDIUMINT(8) NOT NULL DEFAULT '100',
`parent_id` INT(11) NOT NULL,
PRIMARY KEY (`id`),
INDEX `parent_id` (`parent_id`),
CONSTRAINT `FK1` FOREIGN KEY (`parent_id`) REFERENCES `navigation` (`id`) ON UPDATE CASCADE ON DELETE CASCADE
)
COLLATE='utf8_unicode_ci'
ENGINE=InnoDB;
Thank you for your suggestions.