PHP recursive multi-level classification, infinite classification

function getChild($data, $id = 0)
    {
        // Initialize son 
        $child = [];
        // Cycle all data to find $id Son 
        foreach ($data as $key => $datum) {
            // I found my son 
            if ($datum['pid'] == $id) {
                // preserved , Then continue to find his son's son 
                $child[$datum['id']] = $datum;
                // Get rid of yourself first , You can't be your own grandchildren 
                unset($data[$key]);
                // Recursively look for , And put the found son in a child In the field of 
                $child[$datum['id']]['child'] = $this->getChild($data, $datum['id']);
            }
        }
        return $child;
    }

From the Internet, thanks for sharing . Keep it for future use