function disp($pid) {
if (file_exists("pic-".$pid.".JPG")) {
echo "<img src=pic-".$pid.".JPG>";
echo "<br><br>";
if (file_exists("pic-".($pid-1).".JPG")) {
echo "Previous &nbsp; ";
}
if (file_exists("pic-".($pid+1).".JPG")) {
echo "Next";
}
} else {
echo "this file doesn't exist, try here";
}
}
if ($_GET['pid']) {
disp($_GET['pid']);
} else {
disp(1);
}