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PHP Integrating PHP with Databases Limiting Records in SQL Setting LIMITs

Jonathan Grieve
MOD
Jonathan Grieve
Treehouse Moderator 91,253 Points

[SOLVED] Catalog.php is causing chrome to redirect too many times

Hi everyone.

Okay so there's a problem with my catalog.php pages. I've followed the video as best as I can and it seems to be sending the pagination variables but causing redirects.

Can someone with a keener eye than me spot the issue? :)

I've posted the code below and also a link to a Workspace Snaphot. https://w.trhou.se/dqjd7g3u64

catalog.php
<?php 

include("inc/functions.php");


$pageTitle = "Full Catalog";
$section = null;

$total_pages = ceil($total_items / $items_per_page);

//limit results in redirect
$limit_results = "";
if (!empty($section)) {
    $limit_results = "cat=" . $section . "&";
}

// redirect too-large page numbers to the last page
if ($current_page > $total_pages) {
    header("location:catalog.php?"
        . $limit_results
        . "pg=".$total_pages);
}
// redirect too-small page numbers to the first page
if ($current_page < 1) {
    header("location:catalog.php?"
        . $limit_results
        . "pg=1");
}


//determine the offset (number of items to skip) for the current page
//for example: on page 3 with 8 item per page, the offset would be 16

$offset = ($current_page - 1) * $items_per_page;


if (isset($_GET["cat"])) {
    if ($_GET["cat"] == "books") {
        $pageTitle = "Books";
        $section = "books";
    } else if ($_GET["cat"] == "movies") {
        $pageTitle = "Movies";
        $section = "movies";
    } else if ($_GET["cat"] == "music") {
        $pageTitle = "Music";
        $section = "music";
    }
}

$catalog = full_catalog_array(); //include catalog array

if(empty($section)) {
  $catalog = full_catalog_array($items_per_page, $offset);
} else {
  $catalog = category_catalog_array($section, $items_per_page, $offset);
}


include("inc/header.php"); ?>

<div class="section catalog page">

    <div class="wrapper">

        <h1><?php 
        if ($section != null) {
            echo "<a href='catalog.php'>Full Catalog</a> &gt; ";
        }
        echo $pageTitle; ?></h1>

        <ul class="items">
            <?php
            foreach ($catalog as $item) {
                echo get_item_html($item);
            }
            ?>
        </ul>

    </div>
</div>




<?php include("inc/footer.php"); ?>
function.php
<?php
function get_item_html($item) {
    $output = "<li><a href='details.php?id="
        . $item["media_id"] . "'><img src='" 
        . $item["img"] . "' alt='" 
        . $item["title"] . "' />" 
        . "<p>View Details</p>"
        . "</a></li>";
    return $output;
}

function array_category($catalog,$category) {
    $output = array();

    foreach ($catalog as $id => $item) {
        if ($category == null OR strtolower($category) == strtolower($item["category"])) {
            $sort = $item["title"];
            $sort = ltrim($sort,"The ");
            $sort = ltrim($sort,"A ");
            $sort = ltrim($sort,"An ");
            $output[$id] = $sort;            
        }
    }

    asort($output);
    return array_keys($output);
}


function full_catalog_array($limit = null, $offset = 0) {

    include("connection.php");
    try {
          $sql = "
      SELECT media_id, title, category, img 
      FROM Media      
      ORDER BY 
      REPLACE(
        REPLACE(
          REPLACE(title,'The ',''),
          'An ',
          ''
      ),
      'A ',
      '')";      

       if (is_integer($limit)) {
          $results = $db->prepare($sql . " LIMIT ? OFFSET ?");
          $results->bindParam(1,$limit,PDO::PARAM_INT);
          $results->bindParam(2,$offset,PDO::PARAM_INT);
       } else {
          $results = $db->prepare($sql);
       }    
       $results->execute();

          //echo "Retrieved Results: ";
        } catch (Exception $e) {
          echo "Unable to retrieve results: ";
          echo $e->getMessage();
          exit;
        }



    $catalog = $results->fetchAll(PDO::FETCH_ASSOC);
    return $catalog;

}

function get_catalog_count($category = null) {
    $category = strtolower($category);
    include("connection.php");

    try {
        $sql = "SELECT COUNT(media_id) FROM Media";
        if (!empty($category)) {
          $result = $db->prepare(
            $sql
            . " WHERE LOWER(category) = ?"
          );
          $result->bindParam(1,$category,PDO::PARAM_STR);
        } else {
          $result = $db->prepare($sql);
        }
        $result->execute();
    } catch (Exception $e) {
      echo "bad query";
    }

  $count = $result->fetchColumn(0);
  return $count;
}




function random_catalog_array() {
    include("connection.php");

    try {
       $results = $db->query(
         "SELECT media_id, title, category, img 
         FROM Media
         ORDER BY RANDOM()
         LIMIT 4"
       );
    } catch (Exception $e) {
       echo "Unable to retrieved results";
       exit;
    }

    $catalog = $results->fetchAll();
    return $catalog;
}

function category_catalog_array($category, $limit = null, $offset = 0) {
    include("connection.php");
    $category = strtolower($category);
    try {
       $sql = "SELECT media_id, title, category,img 
         FROM Media
         WHERE LOWER(category) = ?
         ORDER BY 
         REPLACE(
           REPLACE(
              REPLACE(title,'The ',''),
              'An ',
              ''
           ),
           'A ',
           ''
         )";

       if (is_integer($limit)) {
          $results = $db->prepare($sql . " LIMIT ? OFFSET ?");
         $results->bindParam(1,$category,PDO::PARAM_STR);
          $results->bindParam(2,$limit,PDO::PARAM_INT);
          $results->bindParam(3,$offset,PDO::PARAM_INT);
       } else {
         $results = $db->prepare($sql);
         $results->bindParam(1,$category,PDO::PARAM_STR);
       }
       $results->execute();
    } catch (Exception $e) {
       echo "Unable to retrieved results";
       exit;
    }

    $catalog = $results->fetchAll();
    return $catalog;
}


function single_item_array($id) {

    include("connection.php");
    try {
          $results = $db->prepare("
            SELECT title, category, img, format, year, publisher, isbn, genre
            FROM Media
            JOIN Genres ON Media.genre_id = Genres.genre_id
            LEFT OUTER JOIN Books 
      ON Media.media_id = Books.media_id
            WHERE Media.media_id = ?"
                           );

      $results->bindParam(1, $id, PDO::PARAM_INT);
      $results->execute();
          //echo "Retrieved Results: ";
        } catch (Exception $e) {
          echo "Unable to retrieve results: ";
          echo $e->getMessage();
          exit;
        }



    $item = $results->fetch(PDO::FETCH_ASSOC);
  if(empty($item)) return $item;   //item return item   - an early return
  try {
          $results = $db->prepare("
              SELECT fullname, role 
        FROM Media_People
        JOIN People ON Media_People.people_id = People.people_id
        WHERE Media_People.media_id = ?"
                           );

      $results->bindParam(1, $id, PDO::PARAM_INT);
      $results->execute();
          //echo "Retrieved Results: ";
        } catch (Exception $e) {
          echo "Unable to retrieve results: ";
          echo $e->getMessage();
          exit;
        }

    while($row = $results->fetch(PDO::FETCH_ASSOC)) {
     $item[$row["role"]][] = $row["fullname"];
    }



    return $item; ///

}
Jonathan Grieve
Jonathan Grieve
Treehouse Moderator 91,253 Points

Problem Solved.

I needed one more piece of code I forgot to include from a previous video. I managed to get the code over to my server which indicated the problem was a division by zero because $items_per_page variable wasn't initialised.

$items_per_page = 8;

if (isset($_GET["pg"])) {
  $current_page = filter_input(INPUT_GET,"pg",FILTER_SANITIZE_NUMBER_INT);
}
if (empty($current_page)) {
  $current_page = 1;
}

$total_items = get_catalog_count($section);