Using PHP to insert into SQL Table with Foreign Keys

Question

I am trying to use PHP to insert data into a SQL table that contains 2 foreign keys. My table is laid out as follows:

title=products 

columns = cart_id, prod_id    // Both columns are foreign keys that come from another table.

I have been able to successfully insert the data in phpmyadmin, but whenever I try to insert inside my php script, I run into errors. The SQL query that phpmyadmin gives is

INSERT INTO `cart_prod` (`cart_id`, `prod_id`) 
                VALUES ('77717', '123456789');

However, when I copy and paste that query into my php code as follows, it does not work.

$conn = conn_create();

$query = "INSERT INTO cart_prod (cart_id, prod_id) 
                        VALUES ('$this->cart_id', '$product_id');";

$result = $conn->$query($query);

Cart id is an attribute of the class that this code is contained within and product_id is a value that is passed through to the class function. I can copy and paste the values directly into my query and that still does not work.

I am using WAMPserver, and when I try to test this section of code, I get the following error:

Fatal error: Call to undefined method mysqli::INSERT INTO cart_prod(cart_id, prod_id) VALUES('77717', '123456789');() in C:\wamp64\www\php\customer.php on line 38

Both of my foreign keys have values in the other tables they are being pulled from. The database does not have a primary key. The way the database is supposed to work is that each row of cart_id will contain a product. All prod_id's associated with a particular cart_id would belong to that cart.

Ex. Database

cart_id prod_id
77717   123456789
77717   987654321
12345   113987454
12345   123456789

Am I doing something wrong with syntax in the query that I seem to be overlooking? Or is it something with the database that needs to be changed such as adding a primary key.

conn_create() is a function I wrote that connects to the database I am using by grabbing my authentication from a file. That function is behaving as expected as I have been able to use it in many other SQL queries I have that are working properly. — Tesla51P
– Tesla51P, Commented Nov 16, 2016 at 0:19

RiggsFolly · Accepted Answer · 2016-11-16 00:17:25Z

1

This is your problem

$result = $conn->$query($query);

Change it to

$result = $conn->query($query);
// -------------^  remove the $

answered Nov 16, 2016 at 0:17

RiggsFolly

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Tesla51P Over a year ago

Thanks that worked. I knew it had to be something simple I was overlooking.

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