PHP: recursively iterating over multi-dimensional array

Question

I have a multi-dimensional array that looks something like this:

Array ( [text] => Level 0-0 => [children] => 
 Array ( 
 [0] => Array ( [text] => Level 1-0 0 => [children] => 
 Array ( 
 [0] => Array ( [text] => Level 2-0 0 => [children] => 
 Array ( 
 [0] => Array ( [text] => Level 3-0 0 ) 
 [1] => Array ( [text] => Level 3-1 0 ) 
 [2] => Array ( [text] => Level 3-2 0 ) 
 [3] => Array ( [text] => Level 3-3 0 ) 
 [4] => Array ( [text] => Level 3-4 0 ) 
 [5] => Array ( [text] => Level 3-5 0 ) ) ) 
 [1] => Array ( [text] => Level 2-1 0 ) 
 [2] => Array ( [text] => Level 2-2 0 => [children] => 
 Array ( 
 [0] => Array ( [text] => Level 3-0 2 ) ) ) 
 [3] => Array ( [text] => Level 2-3 0 ) 
 [4] => Array ( [text] => Level 2-4 0 ) 
 [5] => Array ( [text] => Level 2-5 0 => [children] => 
 Array ( 
 [0] => Array ( [text] => Level 3-0 5 ) 
 [1] => Array ( [text] => Level 3-1 5 ) 
 [2] => Array ( [text] => Level 3-2 5 ) 
 [3] => Array ( [text] => Level 3-3 5 ) 
 [4] => Array ( [text] => Level 3-4 5 ) 
 [5] => Array ( [text] => Level 3-5 5 ) ) ) 
 [6] => Array ( [text] => Level 2-6 0 ) 
 [7] => Array ( [text] => Level 2-7 0 ) 
 [8] => Array ( [text] => Level 2-8 0 ) 
 [9] => Array ( [text] => Level 2-9 0 => [children] => 
 Array ( 
 [0] => Array ( [text] => Level 3-0 9 ) 
 [1] ...
 [10] ...
 [1] ...
Array ( [text] => Level 0-1 => [children] => 
 Array ( 
 [0] => Array ( [text] => Level 1-0 1 => [children] => 
 Array ( 
 [0] => Array ( [text] => Level 2-0 1 => [children] => 
 Array ( 
 [0] => Array ( [text] => Level 3-0 0 ) 
 [1] ...
 [1] ...
 [1] ...
Array ...

And a recursive function that lists out each [text] => Level x-x x

function getTree(array $array) {
 foreach ($array as $key => $value) {
 echo $value['text']."<br>";
 if (!empty($value['children'])) {
 getTree($value['children']);
 }
 }
}
$array = array (...); //array listed above
$tree = getTree($array);
echo $tree;

This gives me a list like this:

Level 0-0
Level 1-0 0
Level 2-0 0
Level 3-0 0
Level 3-1 0
Level 3-2 0
Level 3-3 0
Level 3-4 0
Level 3-5 0
Level 2-1 0
Level 2-2 0
Level 3-0 2
Level 2-3 0
Level 2-4 0
Level 2-5 0
Level 3-0 5
Level 3-1 5
Level 3-2 5
Level 3-3 5
Level 3-4 5
Level 3-5 5
Level 2-6 0
Level 2-7 0
Level 2-8 0
Level 2-9 0
Level 3-0 9
...
...
...
Level 0-1
Level 1-0 1
Level 2-0 1
Level 3-0 0
...
...
...
...

But what I want is the following where each line is indented based on its level:

Level 0-0
 Level 1-0 0
 Level 2-0 0
 Level 3-0 0
 Level 3-1 0
 Level 3-2 0
 Level 3-3 0
 Level 3-4 0
 Level 3-5 0
 Level 2-1 0
 Level 2-2 0
 Level 3-0 2
 Level 2-3 0
 Level 2-4 0
 Level 2-5 0
 Level 3-0 5
 Level 3-1 5
 Level 3-2 5
 Level 3-3 5
 Level 3-4 5
 Level 3-5 5
 Level 2-6 0
 Level 2-7 0
 Level 2-8 0
 Level 2-9 0
 Level 3-0 9
 ...
 ...
 ...
Level 0-1
 Level 1-0 1
 Level 2-0 1
 Level 3-0 0
 ...
 ...
 ...
...

How can I accomplish this?

I've thought about including an incrementing $counter and if statements. Then if (!empty($value['children'])) { $counter++; }. So if counter is 1, add one indent at the beginning of each line. If counter is 2, add two indents, etc. But then I need to decrement $counter-- at the end of every array after iterating over all the children of that array. That's where I'm logically stuck. How can I check if an array is the last array in an array? if (array is last array)) { $counter--; }

Can this solution work? Or is there a better solution I'm not thinking of?

• Nigel Ren: It would help if you gave your array in var_export() format.

Answer 1

A simple way would be to pass in a padding string, when you call the next level add a tab(or you could add spaces if you wish). Then just echo it before your output...

function getTree(array $array, string $pad = '' ) {
 foreach ($array as $key => $value) {
 echo $pad.$value['text']."<br>";
 if (!empty($value['children'])) {
 getTree($value['children'], $pad."\t");
 }
 }
}
getTree($array);

As your getTree() function doesn't return anything, it's not worth capturing the value and displaying it.

As I mentioned in my comment, it would help if you gave your array in var_export() format. That allows easier testing as with your current sample data it's a pain to convert it to an actual array.

• AlexanderGR: Thanks Nigel! This solution is simple and works fine.