You are not checking the result of the call to new mysqli
. If that fails, then $mysqli
will be null and not a valid object you can query against.
Also, by building SQL statements with outside variables, you are leaving yourself open to SQL injection attacks. Also, any input data with single quotes in it, like a name of "O'Malley", will blow up your SQL query. Please learn about using parametrized queries, preferably with the PDO module, to protect your web app. My site http://bobby-tables.com/php has examples to get you started, and this question has many examples in detail.