php query, price change depending on hour of the day - php

Question

i have the following table with values from a sql query:
now depending on the hour of the day, i want to be able to change the values.
for example, its late in the afternoon, i choose the option 3 dagen EUR 20.00. Since right now this day is already almost over, i should pay a smaller amount for 1 dag (example EUR 4), and then the price for 2 dagen EUR 14.00, so at this hour of the day the box 3 dagen should show EUR 18.00
So i know how to get the current hour, but how can i change my query to reflect this?
This is the query i used to get this table:
<?php
echo "<h2>".$lang['pagina3_dagen']."</h2>";
$number=="0";
echo "<table class='prijs'>";
echo "<tr>";
$query="SELECT * FROM $tabel WHERE fietstype='$fietskeuze'";
$result=mysql_query($query) or die ("Ophalen prijzen mislukt: ".mysql_error());
while ($row=mysql_fetch_array($result)) {
$days=$row[days];
$price=$row[price];
if ($days=="1") $writeday=$lang['pagina3_1dag'];
if ($days >="2") $writeday=$lang['pagina3_meerderedagen'];
echo "<td class='prijs'><h2><a href='framemaat.php?lang=".$_SESSION['lang']."&naam=".$naam."&postcodehuisnummer=".$postcodehuisnummer."&fietskeuze=".$fietskeuze."&opties=".$opties."&optieid=".$optieid."&days=".$days."'>".$days." ".$writeday."<br>EUR ".$price."</a><br>";
$number++;
if ($number=="5") {echo "<tr>"; $number="0";}
}
echo "</tr>";
echo "</table>";
?>
i was thinking in pseudo-like code something like this:
$currenthour = date("H", time());
if (($currenthour >="13") && ($currenthour <"15"))
{
$pricedag1=($pricedag1-3eurodiscount);
price in table result for 3 dagen=($pricedag1+$priceofdag2)
}
but how to get the price of the previous day? so the second to last value coming from the query?

Answer 1

I'm not entirely sure I understand the details of your table, but here's a shot:
Why not have a separate table that holds discounts for your products (dagens?) ? This way, you can query your products and join it against the discount table.
// you can decide the data type
CREATE TABLE Discounts (discount_id, product_id, start, end, discount);
then you could left join with your product table
SELECT p.*, d.discount
FROM products p
LEFT JOIN discounts d ON d.product_id = p.product_id
AND start <= ? AND end >= ?;
So after you've received your result set, you can check whether discount is empty or not. If it's not, apply the necessary discount.
if (!empty($row['discount']) {
$price = $price - $row['discount'];
}
Of course, you could take it a step further and determine types of discounts - percentage off, dollar off, etc.