$i=0;
foreach (glob("gallery/*.{jpg,png,gif}", GLOB_BRACE) as $filename) {
if($i == 3) { 
   echo "<tr>
<td class=border>
<img src=\"$filename\" onclick=\"changeImage('$filename')\" width=75 height=75>
</td>";
} elseif ($i==0) { echo"
<tr>
<td class=border>
<img src=\"$filename\" onclick=\"changeImage('$filename')\" width=75 height=75>
</td>";}
$i++;
}