Hoping For Help in Writing This Query in PDO - php

Question

I'm really new to PHP but I've been learning all I can, but I'm also aware that I have a lot to learn so go easy on me.
I'm currently working on a classifieds script and although the code is severely dated, It was a lot worse before I began cleaning it up and now I'm just trying to get the classifieds stable again, then I plan on going back and updating things to a more modern language (PDO) but for now I have NO IDEA on where to begin (and don't want to be reading for months while getting nowhere as I have been while learning HTML, CSS, PHP and JS)
The code below originally displayed the Title column from the table it was fetching the data from (tt_%s) but I have since modified the form which inserts the data into the DB so now there is no longer a "Title" column and in it's place there is now Year and Model from one table and Manufacturer from another table but this is where I get confused and am asking for help.
Presently this is what I am looking at; (Below the code I'll explain more)
<?php
echo "<div class='mostPopular'>";
echo "Popular<br>Listings";
$node = new sqlNode();
$node->table = "types";
$node->select = "ID";
$node->orderby = "ORDER BY rand()";
if(($typeRS = $mysql->select($node)) === false )
die('Unable to Retrieve Ad Type');
$sql = array();
$typeID = 0;
while( $adType = mysql_fetch_assoc($typeRS) ){
$typeID = sprintf("`tt_%s`", abs(intval($adType['ID'])));
$sql[] = sprintf("SELECT %s.Year, %s.Hits, %s.CategoryID, %s.ID, CONCAT('','%s') AS TypeID FROM %s WHERE (`ExpireDate` > NOW()) ",
$typeID,
$typeID,
$typeID,
$typeID,
intval($adType['ID']),
$typeID);
}
$sqlStr = #implode("union ",$sql);
$sqlStr .= " ORDER BY Hits DESC LIMIT 5";
if(($adRS = $mysql->exSql($sqlStr)) === false)
die('Unable to Retrieve Most Popular Ads');
while( $ad = mysql_fetch_assoc($adRS) ){
echo "<p>";
echo "<a href='detail.php?fatherID=".$ad['CategoryID']."&TypeID=".$ad['TypeID']."&ListingID=".$ad['ID']."'>";
echo $ad['Title'];
echo "</a>";
echo "</p>";
}
echo "</div>";
?>
For starters, I don't know what CONCAT('','%s') is all about, nor do I know what $sqlStr = #implode("union ",$sql); is all about.
In addition to these issues, considering that this code is outdated and I should be switching to PDO, I was hoping someone could show me exactly how to perform these queries with PDO as then I could learn by example and apply the same procedures to other queries throughout the site.
If anyone wouldn't mind conversing with me to the point where I can perform the same outcome with PDO I'd be most appreciative and I thank you all in advance while I eagerly await your replies.
BTW, I ask this after studying every PHP and MySql tutorial I can find for the past several months
Thanks

Answer 1

Although "Please rewrite this code to PDO" being too localized one, the real problem you have require different solution.
First of all, you need to fix your database architecture. It's terrible.
Premature optimization, being the root of all evil, depraved you from the right ways. There is no point in splitting your data into small chunks if you going to union them anyway.
You have to have one table for the ads.
It will make all this code obsolete, leaving only one regular query which can be run in one conventional PDO call.
Next, this code has been written by some sprintf() maniac, who made it overcomplicated out of nowhere. As a matter of fact, not a single sprintf() is really needed here.
$sql = array();
while( $row = mysql_fetch_assoc($typeRS) ){
$typeID = abs($row['ID']);
$sql[] = "SELECT Year, Hits, CategoryID, ID, '$typeID' AS TypeID
FROM tt_$typeID WHERE ExpireDate > NOW()";
}
$sqlStr = implode("union ",$sql)." ORDER BY Hits DESC LIMIT 5"
is enough.
But again, no need for this union query. Everything have to be performed via single ordinary query like this one
SELECT Year, Hits, CategoryID, ID, TypeID FROM ads ORDER BY Hits DESC LIMIT 5
which you no doubt will be able to run using whatever PDO example you have