Next image link loop - php

Question

I'm trying to get my next images in a loop so they go back to the start of the the image list. I am able to get the images to go through the list right up to the last image then my last image shows no PID on the link.
I have
<div id="photolistholder">
<?php if(isset($_GET['pid'])){?>
<?php
//Now we'll get the list of the specified users photos
$var =$_GET['pid'];
$sql = "SELECT * FROM coverphotos WHERE coverphoto_id='$var'";
$query = mysqli_query($mysqli,$sql)or die(mysqli_error($mysqli));
while($photo = mysqli_fetch_array($query)){
$user=rawfeeds_user_core::getuser($photo['coverphoto_userid']);
?>
<p class="frontpage_description"><a href="profile.php?username=<?php echo $user['username']; ?>">
<?php
$id=$_SESSION['id'];
if($user['id']){
echo "<img border=\"0\" src=\"userimages/cropped".$user['id'].".jpg\" onerror='this.src=\"img/no_profile_img.jpeg\"' width=\"40\" ><br/>".$user['fullname']."'s</a> Album: </p>";
}else{
echo "<img border=\"0\" src=\"userimages/cropped".$id.".jpg\" onerror='this.src=\"img/no_profile_img.jpeg\"' width=\"40\" ><br/>".$user['fullname']." </a></p>";
}
$id=$_SESSION['id'];
$var = $_GET['pid'] ;
$photo_sql = "SELECT coverphoto_id FROM coverphotos WHERE (coverphoto_id < ".$var." OR coverphoto_id > ".$var.") AND coverphoto_userid = ".$user['id']." ORDER BY coverphoto_id DESC LIMIT 1";
$photo_query = mysqli_query($mysqli,$photo_sql)or die(mysqli_error($mysqli));
$photo_prev=mysqli_fetch_array($photo_query);
if($photo_prev>1){
echo"<a href='coverimagephoto.php?pid=".$photo_prev['coverphoto_id']."'>Previous</a> | ";
}else{
echo " ";
}
$var = $_GET['pid'] ;
$photo_sqls = "SELECT coverphoto_id FROM coverphotos WHERE (coverphoto_id > ".$var." OR coverphoto_id < ".$var.") AND coverphoto_userid = ".$user['id']." ORDER BY coverphoto_id ASC LIMIT 1";
$photo_querys = mysqli_query($mysqli,$photo_sqls)or die(mysqli_error($mysqli));
$photo_next=mysqli_fetch_array($photo_querys);
if($photo_next>1){
echo "<a href='coverimagephoto.php?pid=".$photo_next['coverphoto_id']."'>Next</a>";
}else{
echo "";
}
$user1_id=#$_SESSION['id'];
$user2_id=$user['id'];
if($user1_id==#$_SESSION['id']){
echo " | <a href='include/photo_delete.php?pid=".$photo['coverphoto_id']."'>Delete</a>";
}else{
echo"";
}
?>
<center>
<?php
//echo "<div class='photo_captionholder'><b>Name</b> : ".$photo['photo_name']." | <b>Caption</b> : ".$photo['photo_caption']." |
//<b>Uploaded</b> : ".$photo['photo_datetime']."</div>";
echo "<img id=\"coverimage\" border=\"0\" src='coverimages/".$photo['coverphoto']."?".time()."' onerror='this.src=\"coverimages/nocover.png\"'>";
}}
?>
</body>
I tried using
$var = $_GET['pid'] ;
$photo_sql = "SELECT coverphoto_id FROM coverphotos WHERE (coverphoto_id > ".$var." OR coverphoto_id < ".$var.") AND coverphoto_userid = ".$user['id']."";
$photo_query = mysqli_query($mysqli,$photo_sql)or die(mysqli_error($mysqli));
$photo_next=mysqli_fetch_array($photo_query);
if($photo_next>1){
echo"<a href='coverimagephoto.php?pid=".$photo_prev['coverphoto_id']."'>Next</a> | ";
}else{
echo " ";
}
But the link just jumps between two images. The images are not in 1,2,3,4,5 they can be 1,2,4,5 if a user deletes an image and it can start on image PID 3 or 5.

Answer 1

Would it not be much simpler to code and understand and also reduce your queries (round trips to the server and back) from N+1 queries to 1 query where N=(number of photos) if you just used the first query and then fetched all the results into an array, and then process up and down that array
Quick mockup:
<div id="photolistholder">
<?php
if( isset($_GET['pid']) ) {
// validate the pid
$_GET['pid'] = some_validation_please($_GET['pid']);
$id=$_SESSION['id'];
$sql = "SELECT * FROM coverphotos WHERE coverphoto_id='$_GET['pid']'";
$result = mysqli_query($mysqli,$sql) or die(mysqli_error($mysqli));
$photos = array();
while($row = mysqli_fetch_array($result)){
$photos[] = $row;
}
foreach( $photos as $idx => $photo ) {
// add all your image html with the prev and next links
// using $idx-1 for prev image
// using $idx+1 for next image
// and checking if $idx = 0 for first image
// so you can use count($photos)-1 to know you are on last image
// so you use photos[0] as the next image to get continuous loop
// and if $idx == 0 next image is count($photos)-1
}
?>
Sorry I have not got the time to pick the bones out of what you are putting out to the browser, as I am bound to make a silly mistake and get hassled for it.

Answer 2

I have figured out a better way that works perfectly. Just use a UNION
$var = mysqli_escape_string($_GET['pid']) ;
$photo_sql = "(SELECT coverphoto_id FROM coverphotos WHERE coverphoto_id < ".$var." AND coverphoto_userid = ".$user['id']." AND album=1 ORDER BY coverphoto_id DESC LIMIT 1)";
$photo_sql.= " UNION (SELECT coverphoto_id FROM coverphotos WHERE coverphoto_id > ".$var." AND coverphoto_userid = ".$user['id']." AND album=1 ORDER BY coverphoto_id DESC LIMIT 1)";
$photo_query = mysqli_query($mysqli,$photo_sql)or die(mysqli_error($mysqli));
$photo_prev=mysqli_fetch_array($photo_query);
if($photo_prev>1){
echo"<a href='coverimagephoto.php?pid=".$photo_prev['coverphoto_id']."'>Previous</a> | ";
}else{
echo " ";
}
$var = $_GET['pid'] ;
$photo_sqls = "(SELECT coverphoto_id FROM coverphotos WHERE coverphoto_id > ".$var." AND coverphoto_userid = ".$user['id']." AND album=1 ORDER BY coverphoto_id ASC LIMIT 1)";
$photo_sqls.= " UNION (SELECT coverphoto_id FROM coverphotos WHERE coverphoto_id < ".$var." AND coverphoto_userid = ".$user['id']." AND album=1 ORDER BY coverphoto_id ASC LIMIT 1)";
$photo_querys = mysqli_query($mysqli,$photo_sqls)or die(mysqli_error($mysqli));
$photo_next=mysqli_fetch_array($photo_querys);
if($photo_next>1){
echo "<a href='coverimagephoto.php?pid=".$photo_next['coverphoto_id']."'>Next</a>";
}else{
echo " ";
}