php mysql如何检查多个复选框添加/删除选项和更​​新数据库

I have 3 tables - product, category, product_category.

Table product -> PID , product name

Table category -> CID, category name

Table product_category -> PID, CID

my problem is handling product_category table. Let me explain it in details.

When I add new product, I need to update 2 tables -> product and product_category.

product_category is used to store the product ID and category ID as 1 product can be assigned to multiple categories.

When adding new product, 1 input box plus 1 array to display the categories for user to choose. For example.

foreach($display->category_name as $iid => $name) {

            echo '

                <div class="checkbox">
                    <label><input type="checkbox" name="check_list[]" value="'.$iid.'">'.$name.'</label>
                </div>

                ';
        }

So when clicking on update button, it will show the records that user has keyed in earlier.

So my question is how to check if user has check 1 more option OR uncheck 1 or more option OR remove all of them. And then update table product_category accordingly.

Refer to the screenshot

Case 1 : (this one is easy, just add 1 more option)

Before->Western food and Mix food are checked.

After->Western food , Mix food + Chinese food

Case 2:(remove Western food)

Before->Western food and Mix food are checked.

After->Mix food is checked only.

Case 3:(remove Western food and add Chinese food)

Before->Western food and Mix food are checked.

After->Mix food and Chinese food are checked.

Use array_diff() to get list of unchecked values:

$old_check_list = ['1', '2'];
$new_check_list = ['2', '3'];
$unchecked_values = array_values(array_diff($old_check_list, $new_check_list));

When I'm dealing with checkboxes I usually delete all previous values, then re-insert the new values. This prevents complications:

$mysqli->query("DELETE FROM product_category WHERE product = $id");

foreach ($_GET['check_list'] as $i => $category_id) {
    $mysqli->query("INSERT INTO product_category
            (product_id, category_id) 
        VALUES
            ($id, $category_id)");
}

Please remember to sanitize inputs - do not copy/paste this example.