MySQL and PHP - make href remember previous variable - php

Question

I am quite new to PHP, but come with some knowledge of JavaScript.
I am trying to construct a MySQL table which has sortable columns by header, which I managed figure out through looking around the web, etc; but then wanted the SQL query to use a WHERE clause which only shows rows that meet that clause (and it works), but the problem is that when I then sort the columns it goes back to the original value of the $catergory variable.
I hope that makes sense.
Could somebody please tell me what I am doing wrong and either if I need to change the SQL query or find a way to get the PHP to remember the reassigned value of $catergory, when I want to sort the columns afterwards?
Here is my code:
<?php
// Create connection
$con = mysqli_connect("host","user","password","database") or die("Some error occurred during connection " . mysqli_error($con));
$categoryFilter = array('boardroom', 'staffroom', 'kitchen');
$category = 'boardroom';
if (isset($_GET['categoryFilter']) && in_array($_GET['categoryFilter'], $categoryFilter)) {
$category = $_GET['categoryFilter'];
}
$orderBy = array('Image', 'Description', 'Light', 'Room');
$order = 'Image';
if (isset($_GET['orderBy']) && in_array($_GET['orderBy'], $orderBy)) {
$order = $_GET['orderBy'];
}
?>
<div class="catbuttons">
<ul>
<li>Boardroom</li>
<li style="height: 17px">Staffroom</li>
<li>Kitchen</li>
</ul>
</div>
<div class="index">
<table border='1'>
<tr>
<th>Image</th>
<th>Description</th>
<th>Light</th>
<th>Room</th>
</tr>
<?php
$result = mysqli_query($con,"SELECT * FROM officeindex WHERE Room='".$category."' ORDER BY ".$order)
or die("Error: ".mysqli_error($con));
while($row = mysqli_fetch_array($result)) {
echo "<tr>";
echo "<td>" , $row['Image'] , "</td>";
echo "<td>" , $row['Description'] , "</td>";
echo "<td><img src='" , $row['Light'] , "'></td>";
echo "<td>" , $row['Room'] , "</td>";
echo "</tr>";
}
echo "</table>";
?>
EDIT:
Thank you everyone, I have implemented your suggested solutions to my original question and changed the code above, but I am now having further difficulty. The purpose of my code is to construct an interactive product list of sorts. Now that I have the categories (thanks for pointing out the spelling mistake) working, I want the table, at first, to show all the categories, i.e. all the products in the list, before the user clicks on a specific category.
The other problem is that I can't work out what to do about cells which contain multiple categories (Some products fall into multiple categories).
I've thought about using arrays or loops or booleans or some kind to do both of the above, but my knowledge is limited to JavaScript and I'm a bit lost in PHP, even though there are similarities. Please forgive my ignorance.
I hope I have explained this clearly
Could anyone help me please?

Answer 1

The links in your tableheader only contain the orderBy parameter. If you want to keep the categoryFilter, you need to include it in the href of your headers.
For example:
<tr>
<th>Image</th>
<th>Description</th>
<th>Light</th>
<th>Room</th>
</tr>
For the category filter it's the other way around of course:
<li>Boardroom</li>
<li>Staffroom</li>
<li>Kitchen</li>
Also, as #K.K.Smith pointed out, you might want to replace catergory with category

Answer 2

In your links, You have to put the varaibles if they exists.
Example :
<a href="?categoryFilter=staffroom<?php if isset($_GET['orderBy'] echo '&orderBy=", $_GET['orderBy'];?>" />