php使用子项循环未定义的项目大小

Question

So as an example I have this structure with pages in a website. The thing is I have to get these items in a dropdown list, but they have to intend based on their parent.

• loadSubItems(id) returns the subitems for the id.
• loadSubItems(0) will give the subitems from the root, which in this case is 9, 16, 20
• loadSubItems(9) will give an empty array loadSubItems(16) will return 17, 18, 19

The problem is that the middle loop (the foreach) has to keep on looping as long as there are subitems for that level, print them and for each level an extra intend "_" has to be added.

I have been trying to solve this for hours and I've lost my thinking and I can't seem to figure out what has to happen to be able to do this.

Any help is welcome! Thanks in advance:

Testdata below:

I'm using the following code to go to the second level:

    $items = loadSubItems(0); // returns 9 16 20
    $intend = "";
    foreach($items as $item) {
        $subitems = loadSubItems($item); 
        if(count($subitems) > 0) {
            echo $intend.$item." has subitems: <br />";
            $intend .= "_";
            foreach($subitems as $subitem) {
                echo $intend.$subitem."<br />";
            }
        } else {
            echo "<br />".$item." has no subitems <br />";
        }
    }

This code has output:

9 has no subitems 
16 has subitems: 
_17
_18
_19

20 has no subitems 

edit: So what I want as a result would be:

9 has no subitems 
16 has subitems: 
_17
__21
___22
__23
___24
_18
_19

20 has no subitems

Answer 1

Check out this little function I wrote. It does exactly what you need.. This is the recursive method. You can check it out for any levels.

<?php
function arrayRec($array, $intent) {
    $intent .= "_";
    foreach($array as $key=>$value) {
        echo $intent.$key."</br>";
        arrayRec($value, $intent);
    }   
}
$tree = array("1" => array("11" => array(), "12" => array(), "13" => array()), "2" => array(), "3" => array("31" => array("311" => array()), "32" => array()), "4");
arrayRec($tree);
?>

This results in something like:

_1
__11
__12
__13
_2
_3
__31
___311
__32
_4