问一个用于升序和降序排序操作的查询字符串

EN

<?php  
    if(isset( $_GET['sort'] ) and $_GET['sort'] == 'desc')
        $hide = 'hide';
    else
        $hide = '';
?>
<a href='string_functions.php?sort=desc' class="<?php echo $hide;?>">Sort By Type(DESC)</a>
<?php  
    if( isset( $_GET['sort'] ) and $_GET['sort'] == 'desc' )  {
        $query = "SELECT * FROM `function list` ORDER BY `function type` DESC";
        ?>
        <a href='string_functions.php?sort=asc'>Sort By Type(ASC)</a>
    <?php 
    } else if(isset( $_GET['sort'] ) and $_GET['sort'] == 'asc' ) { ?>
    <?php
        #Read from Database
        $query = "SELECT * FROM `function list` ORDER BY `function type` ASC";
    } else {
        $query = "SELECT * FROM `function list`";
    }
    $data_buffer = $conn -> query($query);
?>

<style>
    .hide {
        display: none;
    }
</style>

<?php
  if( isset( $_GET['sort'] ) and $_GET['sort'] == 'desc')
  {
   $_SESSION['sort_type']='DESC'; //you can set using normal variable also instead of SESSION
   $_SESSION['sort_arrow']='v';
   $_SESSION['sort_link']='asc';
  }
  else
  {
    $_SESSION['sort_type']='ASC';
    $_SESSION['sort_arrow']='^';
    $_SESSION['sort_link']='desc';
  }

  $query = "SELECT * FROM `function list` ORDER BY `function type` '".$_SESSION['sort_type']."'";
  ?>
  <a href="string_functions.php?sort=<?php echo $_SESSION['sort_link'];?>">
   <?php echo $_SESSION['sort_arrow'];?>
</a>

<a href='string_functions.php?sort=desc'>Sort By Type</a>

if(isset( $_GET['sort'] ) and $_GET['sort'] == 'desc') 
    echo "<a href='string_functions.php?sort=asc'>ASC</a>";
else
    echo "<a href='string_functions.php?sort=desc'>DESC</a>";