restrict children count till 6th level in a tree - php

Question

the php function i made gets all the children of a the parent in tree form . The problem is that it gets all the children but i want to restrict it till level 6th of the tree . The code i made is
get_childs("2");
function get_childs($parent_id){
GLOBAL $con;
if ($result = mysqli_query($con,"SELECT * FROM user_profile WHERE referred_by='$parent_id'")) {
echo '<ul>';
while ($row = $result->fetch_assoc()) {
echo '<li>'.$row['user_id'].'';
//call again for each child. if the id dosen't have childs, then prints nothing and go on!
get_childs($row['user_id']);
echo '</li>';
}// end while
echo '</ul>';
}// end if select
}
The output it generates
I want to restrict it till 17 as in above output as the level 6th reaches there .

Answer 1

As per my comment, I'd suggest something like this:
get_childs("2", 0);
function get_childs($parent_id, $level){
GLOBAL $con;
if ($result = mysqli_query($con,"SELECT * FROM user_profile WHERE referred_by='$parent_id'")) {
echo '<ul>';
while ($row = $result->fetch_assoc()) {
echo '<li>'.$row['user_id'].'';
//call again for each child. if the id dosen't have childs, then prints nothing and go on!
if($level < 6)
get_childs($row['user_id'], $level + 1);
echo '</li>';
}// end while
echo '</ul>';
}// end if select
}
With this tiny alteration, your tree will stop as soon as the 6th level is reached. (You might have to tweak it a tiny bit)

Answer 2

get_childs("2", 6);
function get_childs($parent_id, $level){
if($level < 1) return false;
GLOBAL $con;
if ($result = mysqli_query($con,"SELECT * FROM user_profile WHERE referred_by='$parent_id'")) {
echo '<ul>';
while ($row = $result->fetch_assoc()) {
echo '<li>'.$row['user_id'].'';
//call again for each child. if the id dosen't have childs, then prints nothing and go on!
get_childs($row['user_id'], $level--);
echo '</li>';
}// end while
echo '</ul>';
}// end if select
}