getting all downlines left and right and compare them

Question

Hello guys i need to get all the left and right downlines of my left and right. just like this.

   1
 2   3
4 5 6 7

Me: 1 My left & right: 2 & 3

My problem is I have to get all downlines of 2 and downlines of 3 and segregate and compare them.

Compare means i will check if there is user exist under 2 and 3. If 2 has 1 downline and 3 has also 1 downline i will earn 5$.

I try coding this

public static function tree(array $data, &$tree = array(), $level = 0) {
        if (!isset($tree[$level])) $tree[$level] = array();

        foreach ($data as $key => $value) {
            // if value is an array, push the key and recurse through the array
            if (is_array($value)) {
                $tree[$level][] = $key;
                self::tree($value, $tree, $level+1);

            }
            else {
                $tree[$level][] = $value;
            }
        }
    }



public static function testree($parentID = 1) {
    $binary_tree = array(1=>array(2=>array(4,5),3=>array(6,7)));
    self::tree($binary_tree, $output);
}