试图在每个<ul>元素中仅显示4个结果

I have one div class="pdfs" where I want to show some links that will open pdfs.

Inside this div I have two divs, because I want to have one block of pdfs at left and other block at right, like this:

And now Im getting pdfs from database, and it is working fine.

But I just want to show a maximum of 4 pdfs in my <div class="pdfs1">, and If there are more then 4 pdfs I want to show them inside my <div class="pdfs2">, to get this links at right, like I have in my image.

For example, if I have 5 pdfs in database, I want to show 4 in my <div class="pdfs1"> and one in mine <div class="pdfs2">.

Im trying with if condition but it its not working, can you give a little help?

$readPdfs =  $pdo->prepare("SELECT * FROM pdfs");
$readPdfs->execute();

echo '<div  class="pdfs">';
    echo '<h3>Pdfs to see:</h3>';
    echo '<ul class="pdfs1">';
        while ($readPdfsResult = $readPdfs->fetch(PDO::FETCH_ASSOC))
        {
         $folder  = 'pdfs/';
         echo '<li> <a  href="'.$folder.'/'.$readPdfsResult['pdf'].'">'.$readPdfsResult['pdf'].'</a></li>';
        }
    echo '</ul>';

    echo '<ul class="pdfs2">';
         //but here I want to show only if there are more than 4 pdfs
         echo '<li> <a  href="'.$folder.'/'.$readPdfsResult['pdf'].'">'.$readPdfsResult['pdf'].'</a></li>';
    echo '</ul>';
    echo '</div>';
    echo '</div>';
echo '</div>';

Keep track of the number of rows seen so far, and end each UL when 4 have been shown:

$folder  = 'pdfs/';
$rows = 0;

echo '<ul class="pdfs1">';
while (($rows < 4) && ($readPdfsResult = $readPdfs->fetch(PDO::FETCH_ASSOC)))
{
  $fn = htmlspecialchars($readPdfsResult['pdf']);
  echo "<li> <a href='$folder/$fn'>$fn</a></li>";
  ++$rows;
}
echo '</ul>';

$rows = 0;

echo '<ul class="pdfs2">';
while (($rows < 4) && ($readPdfsResult = $readPdfs->fetch(PDO::FETCH_ASSOC)))
{
  $fn = htmlspecialchars($readPdfsResult['pdf']);
  echo "<li> <a href='$folder/$fn'>$fn</a></li>";
  ++$rows;
}
echo '</ul>';