排序列升序/降序：SQL/PHP

Question

There is a mistake causing it not to flip between ASC/DESC and I am 90% sure it is within these few lines.. I think I need to have a "first" loop that will "save" $sort so it flips later. But when I do this it causes an array error then.

The SQL is more than likely correct... I am NOT worried about SQL Injections/PDO/security yet as I am adding that code in later.

Full Link: https://solenoidal-slate.000webhostapp.com/

if(isset($_GET['sort'])){
$sort = $_GET['sort'];
} else {
    $sort='ASC';
}

$sort == 'DESC' ? $sort ='ASC': $sort='DESC';
$query = "SELECT * FROM employees ORDER BY $order $sort";
$results = mysqli_query($con, $query); ?>

<th><a class="column_sort" id="id" href='?order=id&sort=$sort'>ID<span class="glyphicon glyphicon-sort-by-alphabet"></span></a></th>

This above line is an example of a column that is "Getting" the $sort variable.

EDIT: To save time, $order is not the issue.. Each column name is sorting by column successfully.

  if(isset($_GET['order'])){
    $order = $_GET['order'];
    } else {
    $order = 'id';
    } 

Answer 1

Do:

$sort = ($sort == 'DESC') ? 'ASC': 'DESC';

and write only one "&" between query string key/value pairs:

<a ... href="?order=id&sort=$sort">

and apply php code properly in the "href". Otherwise you'll have $sort as html code too.

So, I would do it like so for example:

<?php

$order = isset($_GET['order']) ? $_GET['order'] : 'id';
$sort = isset($_GET['sort']) ? $_GET['sort'] : 'ASC';

$sort = ($sort == 'ASC') ? 'DESC': 'ASC';

$query = "SELECT * FROM employees ORDER BY $order $sort";
$results = mysqli_query($con, $query); ?>
//....
?>

<th>
    <a class="column_sort" id="id" href="?order=id&sort=<?php echo $sort; ?>">
        ID<span class="glyphicon glyphicon-sort-by-alphabet"></span>
    </a>
</th>

Or you could use this directly:

<?php

//...
$sort = ((isset($_GET['sort']) ? $_GET['sort'] : 'ASC') == 'ASC') ? 'DESC' : 'ASC';

$query = "SELECT * FROM employees ORDER BY $order $sort";
//...

Answer 2

Answer:

Your final code would be something like this:

if (isset($_GET['order'])) { // Check $_GET['order'] is in the predefined array
    $order = $_GET['order'];
} else {
    $order = 'id';
} 

if(isset($_GET['sort'])) { // Preferably you can check this also in_array($_GET['sort'], ['ASC', DESC])
    $sort = $_GET['sort'];
} else {
    $sort = 'ASC';
}

$query = "SELECT * FROM employees ORDER BY $order $sort";
$results = mysqli_query($con, $query); 

Update:

Your link needs to be changed,

It should be like this http://solenoidal-slate.000webhostapp.com/?order=id&sort=DESC or ASC and remove one & from the link

Now it's like this: https://solenoidal-slate.000webhostapp.com/?order=id&&sort=$sort