Add function won't work on database - php

Question

Hello everyone I'm studying php + html this semester and I got stuck on this code.
Everything works (list + delete from db) but adding for some reason won't add to the db even though it does validate the inputs and give the code number at the end of URL using the header function. Yes I did include the page that addProduct function at :)
here is the code if anyone can give me an advice or hint
PHP Code:
if ( $action == 'add_product' ) {
$code = $_POST['code'];
$name = $_POST['name'];
$version = $_POST['version'];
$releaseDate = $_POST['releaseDate'];
if (empty($code) || empty($name) || empty($version) || empty($releaseDate)) {
$error = "Please enter a valid and correct values.";
include('../errors/error.php');
exit();
} else {
addProduct($code, $name, $version, $releaseDate);
header("Location: .?code=$code");
}
}
here is the addProduct function
function addProduct($code, $name, $version, $releaseDate){
global $db;
$query = "INSERT INTO products
(productCode, name, version, releaseDate)
VALUES
('$code', '$name', '$version' '$releaseDate')";
$db->exec($query);
}
and this is the HTML Code
<form action="index.php" method="post">
<input type="hidden" name="action" value="add_product"/>
<label>Code:</label> <input type="input" name="code"/>
<br />
<label>Name:</label><input type="input" name="name"/>
<br />
<label>Version:</label><input type="input" name="version"/>
<br />
<label>Release Date:</label><input type="input" name="releaseDate"/> <label>Use 'yyyy-mm-dd' format</label>
<br />
<label> </label>
<input type="submit" name="submit" value="Add Product" />
<br /> <br />
</form>
Thanks :)

Answer 1

Is it just me or you are missing a comma here in your function?
VALUES ('$code', '$name', '$version' '$releaseDate')";

Answer 2

You may use mysql_query($query); instead of $db->exec($query);