Show active category after page load

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Javascript

PHP

jQuery

I have a multi-level category sidebar, created in PHP all work great but when I click any subcategory page load and the sidebar collapse. how can I show the active category after page load using Javascript or PHP?

What I have tried:

<div id="accordian"><br />
   <ul class="nav nav-item d-block" id="nav"><br />
   <?php<br />
   //sidebar category<br />
   $cat_id = get_save_data($connection, $_GET['cat_id']);<br />
   echo multilevel($connection, 0, $cat_id);<br />
   ?><br />
   </ul><br />
</div>

I used a recursive function to fetch the category below is the code

function multilevel($connection, $parent = 0, $cat_id)
{

    $side = '';
    $sql = '';
    if ($parent == 0) {
        $sql =  "SELECT * FROM `categorys` WHERE parent_id = 0 ANd  cats_status = 1 ORDER BY cats_name ASC";
    } else {
        $sql =  "SELECT * FROM `categorys` WHERE parent_id = $parent ANd  cats_status = 1 ORDER BY cats_name ASC";
    }

    $result =  mysqli_query($connection, $sql);

    while ($row = mysqli_fetch_assoc($result)) {
       
        if ($row['parent_id'] == 0) {
            $side .= "<li class='categorys'>
                        <h3>
                            <a href='?cat_id=" . $row['cats_id'] . "' id='" . $row['cats_id'] . "' class='nav-link'>" . $row['cats_name'] . "</a>
                        </h3>";
        } else {
            $side .= "<li class='categorys'>
                        <h3>
                            <a href='?cat_id=" . $row['cats_id'] . "' id='" . $row['cats_id'] . "' class='nav-link'>" . $row['cats_name'] . "</a>
                        </h3>";
        }

        $side .= "<ul class='nav nav-link collapse' id='submenu'>" . multilevel($connection, $row['cats_id'], $row['cats_id']) . "</ul>";
        $side .= "</li>";
    }

    return $side;
}

I tried some jquery, but it's not working properly
https://stackoverflow.com/questions/16288063/jquery-accordion-menu-keep-selected-menu-open