Previous and Next Links

treeleaf20

ALl,
I have a section where I can view private messages on my site. I have them on readmessage.php. What happens on this page is it gets a messageid from the previous page and displays that message. I want to include a next or previous link on the bottom so they don't have to go back to the previous page to view the link. Can someone please help me write the query for this so they can just click on the link to view the next message or the previous message in the database. Thank you for your help in advance.

bpat1434

Well, if you using a "readmessage.php" page and the id is passed via the URL (GET Method) then you could use this:

<?php

$id = $_GET['id'];

$link = 'http://www.domain.com/readmessage.php?id=';

$next = $id++;
$prev = $id--;

$next = $link.$next;
$prev = $link.$prev;

echo '<a href="'.$prev.'">[ Prev ]</a>  ||  <a href="'.$next.'">[ Next ]</a>';

?>

~Brett

wempy

[engaging smart arse mode]

a small bugette has crept in here:

$next = $id++;
$prev = $id--;

if $id=6 before the assignment to $next, after php has performed that statement $id would be equal to 7 ($var++ increments).

I feel it should be:

$next = $id + 1;
$prev = $id - 1;

[disengage smart arse mode]

batman

it's called pagination, do a search and I promise youll get plenty of results....

bpat1434

wempy wrote:
[engaging smart arse mode]

if $id=6 before the assignment to $next, after php has performed that statement $id would be equal to 7 ($var++ increments).
[disengage smart arse mode]

Before stating something like that, why don't you read up on variable incrementation. $I++ is exactly equal to $i+1.

Not to debunk you or anything...

<?php

$id = $_GET['id'];

$link = 'http://www.domain.com/readmessage.php?id=';

$next = $id++;
$prev = $id--;

$next = $link.$next;
$prev = $link.$prev;

echo '<a href="'.$prev.'">[ Prev ]</a>  |Current: '.$id.' |  <a href="'.$next.'">[ Next ]</a>';

?>

Would print ($id == 6):

<a href="readmessage.php?id=5">[ Prev ]</a> | Current: 6 | <a href="readmessage.php?id=7">[ Next ]</a>

~Brett

bpat1434

Wempy, you are half correct. You could use that syntax, or you could use a variation of mine. I messed up. The code should be:

<?php

$id = $_GET['id'];

$link = 'http://www.domain.com/readmessage.php?id=';

$next = $prev = $id;
$next++;
$prev--;

$next = $link.$next;
$prev = $link.$prev;

echo '<a href="'.$prev.'">[ Prev ]</a>  ||  <a href="'.$next.'">[ Next ]</a>';

?>

Thanks for catching it.

~Brett

treeleaf20

One other question I have in your guys code, in my example I have them read the message by the unique field called id. There is another field called userid and a user can only view the messages that they have a userid associated with that record. This is the problem because even if you increment the next link by 1 the next record might not be associated with that userid. A quick example to illustrate this:

Messageid Userid
20 2
21 3
22 2

So if user 2 would click the next link they would try and view messageid 21 but they would actually need to view messageid 22. Please let me know if anyone has a solution for this.

Thank you for your help so far.

bpat1434

grab all associated IDs into an array from your query, and then go up or down the array depending upon where you are and what link you want.

~Brett

treeleaf20

Would that look something like:

$query = "Select messageid from messages where userid='$_SESSION[Userid]'";
$result = mysql_query($query);
$resultset = mysql_fetch_array($result);


echo "<a href=\"$resultset[messageid]++\">Next</a> || <a href=\"$resultset[messageid]--\">Previous</a>";

Thanks

bpat1434

treeleaf20 wrote:

Would that look something like:

$query = "Select messageid from messages where userid='$_SESSION[Userid]'";
$result = mysql_query($query);
$resultset = mysql_fetch_array($result);


echo "<a href=\"$resultset[messageid]++\">Next</a> || <a href=\"$resultset[messageid]--\">Previous</a>";

Thanks

Almost, use the same query, but do this:

while($r = mysql_fetch_array($result)){
    $array[] = $r[messageid];
}

// now, when viewing messages:
for($i=0, $i<count($array); $i++){
    if($array[$i] == $_GET['id']){
        $the_id = $i;
    }
}
$prev = $array[$the_id-1];
$next = $array[$the_id+1];

echo '<a href="readmessage.php?id='.$prev.'">[ Prev ]</a>  ||  <a href="readmessage.php?id='.$next.'">[ Next ]</a>';

~Brett