In documentation I can see ORDER BY expression is usually put at the end of the query, however, in my case, I want to order products by price first and then choose brands, as a result, I would add " AND product_brand IN" after ORDER BY product_price. Then PHP throw an error, i’m pretty sure it is because I put AND express after ORDER BY expression, how can I get over this?

if(isset($_POST['action'])) {
    $keyword =  $_POST['keyword'];
    $output = "";
    $query = "SELECT * FROM $keyword WHERE product_rating = '4.5'";
    if (isset($_POST['general'])) {
        $general_filter = implode("','", $_POST['general']);
        switch ($general_filter) {
            case 'all':
                $query .= "";
                break;
            case 'low_to_high':
                $query .= "ORDER BY product_new_price ASC";
                break;
            case 'high_to_low':
                $query .= "ORDER BY product_new_price DESC";
                break;
            case 'name_ascending':
                $query .= "ORDER BY product_title ASC";
                break;
            case 'name_descending':
                $query .= "ORDER BY product_title DESC";
                break;
            case 'newest':
                $query .= "ORDER BY product_date DESC";
                    break;
            case 'top_seller':
                $query .= "ORDER BY product_sold ASC";
                break;
            case 'available':
                $query .= "AND product_status = '1'";
                break;
        }
    }
    if (isset($_POST['brand'])) {
        $brand_filter = implode(",", $_POST['brand']);
        if ($brand_filter == 'all') {
            $query .= "";
        }
        else {
            $query .= " AND product_brand IN ('$brand_filter')";
        }
    }

I search for hours on internet and still stuck.

>Solution :

SQL has a specific order of commands. It is not allowed to have the orderBy before a WHERE clause.
You can solve this by moving the second if-statement up:

    $query = "SELECT * FROM $keyword WHERE product_rating = '4.5'";
        if (isset($_POST['brand'])) {
                $brand_filter = implode(",", $_POST['brand']);
                if ($brand_filter == 'all') {
                    $query .= "";
                }
                else {
                    $query .= " AND product_brand IN ('$brand_filter')";
                }
        }
        if (isset($_POST['general'])) {
            $general_filter = implode("','", $_POST['general']);
            switch ($general_filter) {
                case 'all':
                    $query .= "";
                    break;
                case 'low_to_high':
                    $query .= "ORDER BY product_new_price ASC";
                    break;
                case 'high_to_low':
                    $query .= "ORDER BY product_new_price DESC";
                    break;
                case 'name_ascending':
                    $query .= "ORDER BY product_title ASC";
                    break;
                case 'name_descending':
                    $query .= "ORDER BY product_title DESC";
                    break;
                case 'newest':
                    $query .= "ORDER BY product_date DESC";
                        break;
                case 'top_seller':
                    $query .= "ORDER BY product_sold ASC";
                    break;
                case 'available':
                    $query .= "AND product_status = '1'";
                    break;
            }
        }