Retrieve and display comments/queries from database - php

Question

I'm developing in php/sql a web application where users will be able to post items that they'd like to sell ( kinda like ebay ). I want non-members to be able to comment on the items or ask queries about items.
My problem is I want to display each item as well as any comment/query made about that item, in a similar manner as the way Facebook wall works.
I want to "append comments"(if any) to each item. The comments table is linked to the items table via column item_id. And the items table is linked to users table via column user_id. I have left joined users table with items table to display item details, i tried to left join comments table as well so that there are 3 joined tables.
That fails because no comments are displayed and only one item is displayed, despite there being multiple entries in each table. Here is the code i,m using.
$database->query
('
SELECT sale.*, query.*, users.id AS userid, users.username as user
FROM sale
LEFT JOIN users ON sale.user_id = users.id
LEFT JOIN query on sale.id = query.item_id
where category = "$category" ORDER BY sale.id DESC
');
$show = " "; //variable to hold items and comments
if ($database->count() == 0) {
// Show this message if there are no items
$show .= "<li class='noitems'>There are currently no items to display.</li>" ;
} else {
$show .= "<li>";
while ( $items = $database->statement->fetch(PDO::FETCH_ASSOC) )
{
$show .= "
//show item details in html
";
while( $query = $database->statement->fetch(PDO::FETCH_ASSOC) )
{
$show .= "
//show queries below item details
";
}
$show .= "</li>" ;
}

Answer 1

Welcome to Stackoverflow!
I recommend you taking a look at pdo. If you are already using mysql_ functions, then I recommend you switch. More on that can be found here.
Now that your pointed to the direction of to what functions to use when connecting/running queries, you now should create your tables. I use phpmyadmin for managing my database, I find it very good, but it's up to you what you use. Once you've decided on the service you use to manage your database, you should then learn how to use it by doing some google searches.
Now you need to set up your table and structure it correctly. If you say you're having items, then you should make a table called items. Next create the columns to the properties of the items. Also I recommend reading about Database Normalization, which is a key aspect of setting up your SQL tables Etc.
Once you have everything set up, you've connected to your database successfully Etc. You now need to set up the "Dynamic Page". What I mean by this is, there's only one page, say called 'dynamic', then a variable is passed to the url. These are called GET HTTP requests. Here's an example of what one would look like: http://example.com/item?id=345.
If you've noticed, you'll see the ? then the id variable defined to 345. You can GRAB this variable from the url by accessing the built in PHP array called $_GET[]. You can then type in your variable name you want to fetch into the []'s. Here's an example.
<?php
$data = $_GET['varname']; // get varname from the url
if(isnumeric($data)){ // is it totally made out of numbers?
$query = "SELECT fieldname FROM table WHERE id=:paramname";
$statement = $pdo->prepare($query); // prepare's the query
$statement->execute(array(
'paramname'=>$data // binds the parameter 'paramname' to the $data variable.
));
$result = $statement->fetch(PDO::FETCH_ASSOC); // grabs the result of the query
$result = $result['fieldname'];
echo 'varname was found in the database with the id equal to:'.$data.', and the result being: '.$result;
}
?>
So now you can see how you can grab the variable from the url and dynamically change the content with-in the page from that!
Hope this helped :)