I realize this is a 'quick and easy' way to connect to MySQL - but it is extremely prone to Sql injection. A parameterized query is a more secure approach. Additionally, the 'mysql' driver should not be used the driver is deprecated and will not exist in php7. Instead, MySQLi or PDO driver(preferred) for sql is to be used. The MySQL_connect is no longer documented on the PHP website.
Even if this is a test environment, I would strongly encourage switching to a secure driver early.
As Elias Nicolas pointed out... Placing the @ symbol in front of mysql_connect causes any error you are having to be 'skipped'. The error won't log, and it will make it look like there isn't a problem when there is.
Edit: This will get you close to Mysqli - should already exist in the extensions for php. You might need to enable it in the php.ini. Also, you might need single ' marks around the ?'s. i.e: ('?').
// don't forget to sub the vars!
$db_host = "host";
$db_username = "user_name";
$db_pass = "password";
$db_name = "db_name";
$link = new mysqli($db_host, $db_username, $db_pass, $db_name) or die ('Could not connect to the database server' . mysqli_connect_error());
$sql = <<<QUERY
INSERT INTO signups
(FirstName, LastName, email, CompanyName, JobTitle, ProductSector, ProductWebsite, ProductName, id)
VALUES
(?,?,?,?,?,?,?,?,?);
QUERY;
if ($stmt = $mysqli->prepare($sql))
{
$stmt->bind_param("sssssssss", $FirstName, $LastName, $email, $CompanyName, $JobTitle, $ProductSector, $ProductWebsite, $ProductName, $id);
$stmt->execute();
}
$link->close();