Some misunderstanding with pagination

Question

I am trying to make pagination from one post to the next post in a single blog post. The problem is that when I open an article with ID-1 and I click on the 'next' button I get a blank/empty page.

This is the post page, which gets the ID of the chosen post in blog.php. This is what I have so far. Any suggestions?

<?php
     // include database connection
     require_once 'database.inc.php';
     $pdo = Database::connect();
       if(isset($_GET['post_id']) && is_numeric($_GET['post_id'])){
                $post_id = $_GET['post_id'];
     // page is the current page, if there's nothing set, default is page 1
     $page = isset($_GET['page']) ? $_GET['page'] : 1;

     // set records or rows of data per page
     $recordsPerPage = 1;

     // calculate for the query LIMIT clause
     $fromRecordNum = ($recordsPerPage * $page) - $recordsPerPage;

     // select all data
     $query = "SELECT * FROM posts WHERE post_id = $post_id LIMIT {$fromRecordNum}, {$recordsPerPage}";

     $stmt = $pdo->prepare( $query );
     $stmt->execute();

     //this is how to get number of rows returned
     $num = $stmt->rowCount();

     //check if more than 0 record found
     if($num>0){                           
            while ($row = $stmt->fetch(PDO::FETCH_ASSOC)){               

                     echo ' 
                           // post body ';     
                }
    }                                                 

         // *************** <PAGING_SECTION> ***************

             // ***** for 'first' and 'previous' pages
             if($page>1){       
                 // ********** show the previous page
                 $prev_page = $page - 1;
                 echo "
                <a href='" . $_SERVER['PHP_SELF'] . "?page={$prev_page}'>
                    <div class='prev-btn control-nav text-left'>
                        <h5>Previous Post</h5>
                    </div>
                </a>";     
             }
             // find out total pages
             $query = "SELECT COUNT(*) as total_rows FROM posts";
             $stmt = $pdo->prepare( $query );
             $stmt->execute();

             $row = $stmt->fetch(PDO::FETCH_ASSOC);
             $total_rows = $row['total_rows'];

             $total_pages = ceil($total_rows / $recordsPerPage);

             if($page<$total_pages){
                 // ********** show the next page
                 $next_page = $page + 1;
                 echo "<a href='" . $_SERVER['PHP_SELF'] . "?page={$next_page}'>
                    <div class='next-btn control-nav text-right'>
                        <h5>Next Post</h5>
                    </div>
                </a>";
             }
}
?>                       

Answer 1

Could you show it in a working website? It would be easier to tell what is wrong then, but from the code it looks like you are making the url wrong in your anchor href part.

$prev_page = $post_id - 1;
<a href='" . $_SERVER['PHP_SELF'] . "?post_id={$prev_page}'>
               <div class='prev-btn control-nav text-left'>
                   <h5>Previous Post</h5>
               </div>
           </a>"

$next_page = $post_id + 1;

and the link is there made in same manner as previous one

as i am not sure what your server php self is returning and you shouldnt be adding the second ? symbol in it, if it already had it and u should use & i think for get parameters as ? is only used once after the script file name once. Or you are either missing the ID in your url.

Also blank/empty page might be crashing the script on that page and if u have errors turned off you wont see it in webpage and will have to go to your php errors log file to look for them

EDIT: as block quote wasnt showing correctly.

Answer 2

It's not very clear from your question, but I think your problem is this, your code requires the post_id parameter to be set:

if(isset($_GET['post_id']) && is_numeric($_GET['post_id'])){
    $post_id = $_GET['post_id'];
}

But in your next and prev page links, you're not setting a post_id parameter:

echo "<a href='" . $_SERVER['PHP_SELF'] . "?page={$next_page}'>
    <div class='next-btn control-nav text-right'>
        <h5>Next Post</h5>
    </div>
</a>";

Your code is inherently relying on a single post being shown, as determined by the post_id. Here's what I suggest, change:

 // select all data
 $query = "SELECT * FROM posts WHERE post_id = $post_id LIMIT {$fromRecordNum}, {$recordsPerPage}";

to:

 // select all data
 $query = "SELECT * FROM posts LIMIT {$fromRecordNum}, {$recordsPerPage}";

of course, then, you won't be able to show a specific post, but then again it's hard to know what you're actually trying to achieve here.

Answer 3

It is because first you get $post_id but then in the links you put $page which doesn't contain your ID. Try to change your nex&prev links like this:

<a href='" . $_SERVER['PHP_SELF'] . "?post_id=".$prev_page."'>
<a href='" . $_SERVER['PHP_SELF'] . "?post_id=".$next_page."'>

Also don't forget to change the line for $page here:

$page = isset($_GET['page']) ? $_GET['page'] : 1;

to this

$page = isset($_GET['post_id']) ? $_GET['post_id'] : 1;

This should do the trick.