MySQL - Return generated AUTO_INCREMENT value on INSERT

Question

Hopefully an easy one - I can't work out a robust solution.

I'm building a cart mechanism which generates a id_cart AUTO_INCREMENT Primary Key. The cart item has another table with cart product variables like size. I want to attribute the same id_cart in the size table.

CREATE TABLE
-> id_size_cart NOT NULL PRIMARY KEY AUTO_INCREMENT,
-> id_cart //THIS WILL BE THE AI value from the product cart
-> size_name

I've seen SELECT LAST_INSERT_ID().

How solid will this be to ensure it's the last inserted ID? Don't want customers getting the wrong size!

__ EDIT ___

Thank you for the input. Still, I'm having trouble. See actual code below;

//add product to cart table
$addtocart_sql = "INSERT INTO store_cart (id_cart, id_session) VALUES ('', '".$_COOKIE["PHPSESSID"]."')";
$addtocart_res = mysqli_query($dbConnect, $addtocart_sql) or die(mysqli_error($dbConnect));

$last_row_id = mysqli_query($dbConnect, "SELECT LAST_INSERT_ID()") or die(mysqli_error($dbConnect));

echo 'INSERT worked!<br/>';
echo $last_row_id;

Error shows as

Parse error: syntax error, unexpected T_STRING in /websites/LinuxPackage05/4v/35/xy/4v35xy-55415.webfusion-hosting.co.uk/public_html/noff-group.com/dev/add_to_cart.php on line 27

Thanks in advance.

Answer 1

From the manual:

For LAST_INSERT_ID(), the most recently generated ID is maintained in the server on a per-connection basis. It is not changed by another client. It is not even changed if you update another AUTO_INCREMENT column with a nonmagic value (that is, a value that is not NULL and not 0). Using LAST_INSERT_ID() and AUTO_INCREMENT columns simultaneously from multiple clients is perfectly valid. Each client will receive the last inserted ID for the last statement that client executed.