Random pictures in two pages - php

Question

I have a table that stores images of three categories: cars, bikes, buses. These images appear on two pages. On the first page, you should see an image of each category, defined so random. On the second page, you should see the remaining pictures. How can I do this using php?

Answer 1

I would prefer to do this in MySQL, you can set the order to:
ORDER BY MD5(ImageNo+UserRandomNumber)
SQL FIddle
You can generate a single random number per user, store this in the session then apply this to the ordering and as long as the number supplied stays the same, the order will remain the same too.

Answer 2

You can indeed use a session to store which images were shown on the first page, and then leave them out on the second page. Without knowing your exact table structure, something like this should work:
<?php
// page 1
session_start();
function get_random_image_id($category)
{
// SELECT id FROM images WHERE category = $category ORDER BY RAND() LIMIT 1
}
function show_image($id)
{
// SELECT * FROM images WHERE id = $id
// echo <img ...>
}
$_SESSION['image_ids'] = array(
get_random_image_id("cars"),
get_random_image_id("bikes"),
get_random_image_id("buses"),
);
foreach($_SESSION['image_ids'] as $image_id)
{
show_image($id);
}
?>
<?php
// page 2
session_start();
function show_images($exclude_ids)
{
$ids = implode(",", $exclude_ids);
// SELECT * FROM images WHERE id NOT IN ($ids)
}
$exclude = array();
if(isset($_SESSION['image_ids'])) // has the user visited page 1?
{
$exclude = $_SESSION['image_ids'];
}
show_images($exclude);
?>