What Does =? Do?

In the authentication, there’s this:

$user = User::model()->find('LOWER(username)=?', array(strtolower($this->username)));

What does =? do in this section: LOWER(username)=?

It’s an interpolation placeholder, it gets replaced by the contents of strtolower($this->username).

See example 2 here: PHP: Prepared statements and stored procedures

Thank you.

Seems like it’s good feature to take advantage of.