pset7: buy.php keeps INSERT-ing the same stock into my database

Question

Like it says on the tin: all of a sudden I can only buy stocks of a single company in pset7. For example, I logged in as John Harvard, and bough 10 shares of Google. I then tried to buy 10 shares of a different company, but instead I had another 10 shares of Google added to my portfolio.

I find this strange, because when I var_dump-ed the variables that I am using in the INSERT statement, they all printed out just as they should be.

The (I hope) relevant snippet of my code is here:

$insert = CS50::query("INSERT INTO portfolios (users_id, symbol, shares) VALUES(?, ?, ?) ON DUPLICATE KEY UPDATE shares = shares + VALUES(shares)", $_SESSION["id"], $stock["symbol"], $_POST["shares"]);

I don't know if this is relevant, but I have implemented the joint key mentioned in the pset spec in my database (so users_id and symbol were together marked as unique).

I've been on this for some time, and tried implementing the above statement in a few different ways, so I'll appreciate help.

EDIT: this is what my 'portfolios' table looks like:

+----------+------------------+------+-----+---------+-------+
| Field    | Type             | Null | Key | Default | Extra |
+----------+------------------+------+-----+---------+-------+
| id       | int(10) unsigned | NO   | PRI | NULL    |       |
| users_id | int(10) unsigned | NO   | MUL | NULL    |       |
| symbol   | varchar(255)     | NO   |     | NULL    |       |
| shares   | int(10) unsigned | NO   |     | 0       |       |
+----------+------------------+------+-----+---------+-------+

Answer 1

Solved this now (after a veeeery long day).

The problem was indeed with my database: I forgot to add auto-increment to id, so the database went a bit crazy when inserting.

Answer 2

$stock["symbol"] does not come from the $_POST superglobal variable. It's generated elsewhere by a call to lookup(). Look at that section of your code to see why it's returning GOOG every time.

EDIT: I edited my answer to say $_POST instead of $_GET, and lookup() instead of query(). But yeah ... if the value of $stock["symbol"] really is changing appropriately based on the user input submitted via $_POST, then I'm stumped.

Do me a favor. Open a new Terminal tab in the CS50 IDE, and execute the following commands:

mysql50 shell
USE `pset7`;
DESCRIBE `portfolios`;
exit

I have a hunch that you are triggering a duplicate purchase on the users_id field somehow, which is causing it to add the value of the shares to the only line in the portfolios table that matches that users_id.