PHP按升序/降序排序不起作用

Question

I'm designing a simple task list, but I encountered a little problem. I want to be able to order the items from the database by clicking on a form button, but it is not working.

This is the code for ordering it between Ascending and Descending.

$type='ASC';
if(isset($_POST['sort'])) {
    if ($type == 'DESC') {
         $type = 'ASC';  
    }
}elseif($type == 'ASC') {
    $type='DESC';  
}

The query for getting results from the DB:

$sql = 'SELECT * FROM customers ORDER BY id '. $type;

(EDIT: button is inside form tags with post method) and the form button:

<form method="post"><button type="submit" name="sort" id="asc"></button></form>

This (in my opinion) should be able to work, but it doesn't. anyone willing to help me find the problem?

Answer 1

Or you can use AJAX .

$("body").on("click", "#asc", function(e) {
 e.preventDefault();
 sort();
});

function sort() {
  var order = find("table#sort_order").val();

  $.ajax({
    url: 'process.php',
    type: 'POST',
    data: order,
    dataType: 'json',
    success: function(data) {
       // change sort order using data
    }, // End of success function of ajax form
    error: function(xhr, status, errorThrown) {
      console.log("Error: " + errorThrown);
      console.log("Status: " + status);
      console.dir(xhr);
    },
  }); // End of ajax call 
}

Answer 2

if you want to use form, you need to save the value to input type="hidden".

<?php
 $type = $_POST["sortvalue"];
 if(!$type) {
     $type = "ASC";
 }
 if(isset($_POST['sort'])) {
     if ($type == 'DESC') {
         $type = "ASC";
     }elseif($type == 'ASC') {
         $type = "DESC";
     }
 }
$sql = 'SELECT * FROM customers ORDER BY id '. $type;
?>

<form method="POST">
<button type="submit" name="sort" value="sort">Sort</button>
<input type="hidden" name="sortvalue" value="<?php echo $type; ?>">
</FORM>

hope this work for you.. :D