Order by based on user selection - php

Question

I have a search box which a user can search their favorite cases. I have ordered the search results by date, but I want to make it optional for a user and they can choose it by themselves:
$orders = array("date","price"); //field names
$key = array_search($_GET['sort'],$orders)); // see if we have such a name
$orderby = $orders[$key]; //if not, first one will be set automatically. smart enuf :)
$quer = "SELECT*FROM ".$db_table." WHERE
`case`=
'apartment'
AND `field`=
'sell'
ORDER BY
$orderby";
$query=mysqli_query($connect,$quer)
or die(mysqli_error());
?>
<?php while($row = mysqli_fetch_array($query)):
echo "price ";
echo "address ";
//to simplify the code I do not write the rest
?>
<?php endwhile;?>
For example, order by date or price or other things. How can I do it?
Users can get values from dropdownlist:
<select>
<option value="date">order by date</option>
<option value="price">order by price</option>
</select>

Answer 1

Here one example of have you can get this by allowing user to choose order by what and even in whether ASC/DESC (this is also immune to MySQL injections because of set code values). You can remove checkbox if not needed but then don't forget to remove that part in query too:
if (!empty($_POST['dropdownOption']))
{
$orderBy = ($_POST['orderValue'] == "date") ? "date" : "price";
$orderType = (!empty($_POST['orderType'])) ? "DESC" : "ASC";
$quer = "SELECT * FROM TABLE WHERE `case` = 'apartment' AND `field` = 'sell' ORDER BY ".$orderBy." ".$orderType."";
$query = mysqli_query($connect, $quer) or die(mysqli_error());
}
?>
<form method="post" action="">
<select name="orderValue">
<option value="date">order by date</option>
<option value="price">order by price</option>
</select><br>
<input type="checkbox" name="orderType" value="1">In descending order?</input><br>
<input type="submit" name="dropdownOption" value="Apply">
</form>
Note that I gave this as a form (because I'm not informed how your website looks like and I don't know if you're Ajax or something else. If you're Ajax, then you need to make small changes, actually). With the help of CSS, you can achieve this as if it is just a select menu.