PHP recursive function inside foreach loop is adding up previous data within next loop

I am looping through some locations, and then calling a recursive function to get these locations categories and sub categories. What is happening that the function returns data as a combination of previous loop result. How can I get rid of this, please help me on this my code looks like this.

foreach ($data as $row) {
   $get_options = categoryWithSubcategories(0, 0,$row['location_id'],$dbConn);
   // here I am passing $row['location_id'] to this function, but it merge prvious data within next loop.
}

Recursive function is below.

function categoryWithSubcategories($current_cat_id, $count,$locationId,$dbConn)
{
    static $option_results;
    // if there is no current category id set, start off at the top level (zero)
    if (!isset($current_cat_id)) {
        $current_cat_id =0;
    }
    // increment the counter by 1
    $count = $count+1;
    // query the database for the sub-categories of whatever the parent category is
    $sql =  "SELECT cat_id, cat_name from tbl_category where cat_parent_id = $current_cat_id and locationid=$locationId and delete_flag='0'";
    $stmt =  $dbConn->prepare($sql);
    $result =$stmt->execute();
    $data = $stmt->fetchAll();
    $num_options = $stmt->rowCount();
    if ($num_options > 0) {
        foreach ($data as $categoryList) {
            // if its not a top-level category, indent it to
            //show that its a child category
            if ($current_cat_id!=0) {
                $indent_flag =  ' ';
                for ($x=2; $x<=$count; $x++) {
                    $indent_flag .=  ' >> ';
                }
            }
            $cat_name = $indent_flag.$categoryList['cat_name'];
            $option_results[$categoryList['cat_id']] = $cat_name;
            // now call the function again, to recurse through the child categories
            categoryWithSubcategories($categoryList['cat_id'], $count,$locationId,$dbConn );
        }
    }
    return $option_results;
}