How to return multiples lines in a shortcode?

Don’t use output buffering. It is too slow and sometimes hard to debug. Use heredoc.

Example:

$output = <<<MYUNIQUENAME
    <div>$foo
      <p>Some $bar</p>
    </div>
MYUNIQUENAME;

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