PHP Loop within a loop after x do x

Get rid of this:

$i = 5;

Set $i to zero before each inner loop:

while($row = mysql_fetch_array($result))
{  
    $i = 0;

And then abort the inner loop if $i hits 5:

echo '<a href="/product-sale.php?prodref='.$vpxd. ...
if (++$i == 5) {
    break;
}

If I'm reading that right, you want to have multiple <ul> with at most 5 <li> each?

$i = 0;
while(...) {
   if (($i % 5) == 0) {
      echo '<ul>';
   }
   .... stuff ...
   if ((($i + 1) % 5) == 0) {
      echo '</ul>';
   }
   $i++;
}

The first if() will open a new list anytime you've reached a multiple of '5' on the $i counter. So for the i=0, you get a UL. Then it simply outputs individual <li> elements and increments $i until it reaches 4. At that point you've output 5 li elements, and it'll now output a </ul> to close the list.

Are you searching for the break statement?

while($row = mysql_fetch_array($result))
{    
  $i = 0;

  $pid = $row["stock_products_code"];
  $dir = "assets/sale/$pid/";
  $dh = opendir($dir);

  echo '<li class="royalSlide">'; 

  while (($file = readdir($dh)) !== false)
  {       
    $vpxd = $file;

    if($vpxd != "." && $vpxd != ".." )
    {
      $vpxd=str_replace(".jpg","", $vpxd);
      echo '<a href="/product-sale.php?prodref=$vpxd" target="_top"><img src="/assets/sale/$pid/$file" border="0" /></a>';
      $i++;
    }

    if ($i == 5) 
    {
      break; // leave the inner while loop
    }

  }

  echo '</li>';   

  closedir($dh);
}