Create nested list from Multidimensional Array

Question

I have an array in PHP, which looks like this:

array (
    [0] => array (
        [id] => 1
        [title] => \"Title 1\"
        [parent_id] =>         


        

Answer 1

You should use recursion:

First the array in 'php' syntax:

 array (
        'id' => 1,
        'title' => "Title 1",
        'parent_id' => 'NULL',
        'depth' => 0
    ),
    '1' => array (
        'id' => 2,
        'title' => "Title 2",
        'parent_id' => 'NULL',
        'depth' => 0
    ),
    '2' => array (
        'id' => 3,
        'title' => "Title 3",
        'parent_id' => 2,
        'depth' => 1
    ),
    '3' => array (
        'id' => 4,
        'title' => "Title 4",
        'parent_id' => 2,
        'depth' => 1
    ),
    '4' => array (
        'id' => 5,
        'title' => "Title 5",
        'parent_id' => 'NULL',
        'depth' => 0
    ),
    '5' => array (
        'id' => 6,
        'title' => "Title 6",
        'parent_id' => 4,
        'depth' => 0
    )
);

Here the code:

$level = 'NULL';

function r( $a, $level) {
   $r = "
";
   foreach ( $a as $i ) {
       if ($i['parent_id'] == $level ) {
          $r = $r . "
" . $i['title'] . r( $a, $i['id'] ) . "
";
       }
   }
   $r = $r . "
";
   return $r;
}

print r( $a, $level );

?>

The results:

Title 1
Title 2
Title 3

Title 4
Title 6
Title 5

1. Title 1\n
2. Title 2\n
   1. Title 3\n
   2. Title 4\n
      1. Title 6\n
3. Title 5\n

EDITED AFTER CHECK AS SOLUTION

To avoid empty leafs:

function r( $a, $level) {
   $r = '' ;
   foreach ( $a as $i ) {
       if ($i['parent_id'] == $level ) {
          $r = $r . "
" . $i['title'] . r( $a, $i['id'] ) . "
";
       }
   }
   return ($r==''?'':"
". $r . "
");
}