使用php的递归函数在二叉树中获取级别

Question

I want to get level in the binary tree. I am getting already tree and insertion point but there is a problem in getting pair matching and level. The binary tree image is attached here

how to stop recursive function after level 3.

my code is given below

function getTree($parent_id, $level){
  global $conn;
  $sql2 = "SELECT * FROM user WHERE parent_id='".$parent_id."' ORDER BY `rightorleft`";
  $result2 = $conn->query($sql2);
  $i=0;
  static $calls=0;
  if (mysqli_num_rows($result2) > 0)
  {
    echo "<ul>";
    while ($row2 = mysqli_fetch_object($result2))
    {
        echo '<li>';
        echo '<div><a href="#"><img src="images/user.png" width="40" height="40"><br>'.$row2->user_id.'</a></div>';
        getTree($row2->id,$level++);   
        echo '</li>'; 
    }
    echo "</ul>";
   }
}

I want to result only for 2 level like this

Answer 1

Try using $level as a counter to stop the recursion calls.

By calling the function with $level = 3 should give you the desired result.

function getTree($parent_id, $level)
{
    global $conn;

    // Stop when $level is 0 or less
    if($level <= 0) return ;

    $sql2 = "SELECT * FROM user WHERE parent_id='".$parent_id."' ORDER BY `rightorleft`";
    $result2 = $conn->query($sql2);
    $i = 0;
    static $calls = 0;
    if (mysqli_num_rows($result2) > 0)
    {

        echo "<ul>";
        while ($row2 = mysqli_fetch_object($result2))
        {
            echo '<li>';
            echo '<div><a href="#"><img src="images/user.png" width="40" 
            height = "40" >< br > '.$row2->user_id.' </ a ></ div > ';

            // Recursively go deeper, use $level-1 here
            getTree($row2->id,$level-1);
            echo '</li>';
        }
        echo "</ul>";
    }
}