display Category as (ul) item & Subcategory as (li) item in php

Question

function showcategory($parentid)
{
     $sql = "select * from categories where parent_id='".$parentid."'";
     $result = mysqli_query($GLOBALS['conn'],$sql);
     $output ="<ul id ='tree1' >\n";
    while($data=mysqli_fetch_array($result))
    {
        $output.="<li>\n".$data['name'];
        $output.=showcategory($data['id']);
        $output.="</li>";
    }
    $output.="</ul>";
    return $output;
}

I have a treeview created using PHP, and the function that extracts the treeview extracts the category and its subcategory properly. The categories table in the database has a column that holds the specified values (1/0) where 1 is for main categories and 0 is for subcategories. The problem I face is that when I extract the categories from the database, there is no distinction between whether the categories are main or subcategories. They are all displayed as li elements, and I use CSS formatting on the treeview to create a folder icon on the list items. The problem is how to display the main categories that have a value of 1 in the categories table as an ul element that contains a folder icon that can be opened to show what's inside, and the subcategories that have a value of 0 in the categories table should be displayed as li elements without any folder icon (meaning that only the subcategory name is displayed as text).

my output

I need to get outputs as shown in this image.

Answer 1

I suggest you to query into database only one time other than put DB query in a recursion function.

Take you needs to check where a menu item is main (base on type value 0/1). This add class='main' to main item and you can use css to style the main icon. Let's try this modification.

function showcategory($data, $parentId = 0) {
$menu = '<ul>';

foreach ($data as $item) {
    if ($item['parent_id'] == $parentId) {
        $menu .= '<li';
        
        // Add 'main' class if 'type' is 1
        if ($item['type'] == 1) {
            $menu .= ' class="main"';
        }

        $menu .= '>';
        $menu .= '<a href="#">' . $item['name'] . '</a>';
        
        // Recursive call to build sub-menu if it has children
        $submenu = showcategory($data, $item['id']);
        if ($submenu) {
            $menu .= $submenu;
        }

        $menu .= '</li>';
    }
}

$menu .= '</ul>';

return $menu;
}

$sql = "select * from categories where parent_id='".$parentid."'";
$result = mysqli_query($GLOBALS['conn'],$sql);
$data=mysqli_fetch_array($result)

$menu = showcategory($data);
echo $menu;