How can I make sure that PDO's lastInsertId() is not that of another simultaneous insert?

Question

I am doing a signup form with an INSERT SQL query using PDO. After this INSERT, I want to extract the userid (auto incrementing, primary key) that

Answer 1

lastInsertId() returns the identifier of the last row inserted on that connection, so concurrent users (with different connections to the database) will not interfere.

Answer 2

You can avoid this by doing a select by the email or some unique field. That will guarantee you get the correct user id.

For example:

select id from user_table where email = 'user@email.com' limit 1;