While loop not working as expected with variable

The following code works fine when i remove the && $f<4 , but with it in, it doesn't work.

PHP:

$titles=array();

$f=0;

while ($row=mysql_fetch_assoc($query) && $f<4){  //this line doesn't work

        $titles[]=$row['questiontitle'];

            echo "<div class='questionPreview'>$titles[$f]</div>";

            $f++;

        }