How to know if user logged in

<?php
if ( is_user_logged_in() ) {
  echo '<script type="text/javascript">var logged_in=true;</script>';
} else {
    echo '<script type="text/javascript">var logged_in=false;</script>';
}
?>

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)