Description:
------------
1. Create array and store it in $_SESSION, eg.
2. Write method which goes trough all elements of new structure searching for particular element (use foreach), and when founds it, call very same function looking for other element. Take a look at a code.
Work perfectly on Linux. On Windows function looses state (index) of foreach, so you have to change line:
foreach($_SESSION['application'] as $key => $value) {
to
$foo = $_SESSION;
foreach($foo as $key => $value) {


Reproduce code:
---------------
$_SESSION['application'] = array(
   array( 'name' => 'l1', 'symbol' => 'l1', 'father' => 'root'),
   array( 'name' => 'l1-1', 'symbol' => 'l1-1', 'father' => 'l1'),
   array( 'name' => 'l1-2', 'symbol' => 'l1-2', 'father' => 'l1'),
   array( 'name' => 'l2', 'symbol' => 'l2', 'father' => 'root'),
 );
function getTreeNodes($father) {
  $ret = array();
  foreach($_SESSION['application'] as $key => $value) {
    if($value['father'] == $father) {
      $child = array( 'symbol' => $key, 'name' => $value['name'],	'child' => array());
      $child['child'] = $this->getTreeNodes($key);
      $ret[] = $child;
    }
  }
  return $ret;
}
$tree = array();
$tree[] = array( 'symbol' => 'root', 'name' => 'Aplikacje', 'child' => array() );
$tree[0]['child'] = $this->getTreeNodes('root');
print_r($tree);


Expected result:
----------------
array of arrays (tree)
root
 - l1
   - l1-1
   - l1-2
 - l2

Actual result:
--------------
array of arrays (one branch)
root
 - l1
   - l1-1