PHP使用ORDER BY查询MySQL对数据库项进行排序

Question

我有一个MySQL数据库，用于动态填充网页。 我正在构建一个MySQL查询，该查询将获取一些存储在称为products的表中的products ，以后可以使用PHP在页面上回显这些products 。 该表中的列是id ， product_name ， price和description 。 我希望用户能够通过单击页面上的相关链接，按价格，价格（低-高）等字母顺序对产品进行排序。 到目前为止，这是我写的：

// Run a SELECT query to get all the products stored in the database
// By default, if no sorting URL variable is fed into the page, then the SQL query becomes order by id.
// The first time you land on the index page as plain index.php, not index.php?=variable, this is the query that's used

$sql = mysqli_query($con,"SELECT * FROM products ORDER BY id DESC");

// If the user chooses to sort the produts in a different way, then an HTML link will set a PHP variable into this page
// We will check for that variable and change the SQL query to sort the products in a different way
if (isset($_GET['sortby'])) {
  // Capture that in a variable by that name
  $sortby = $_GET['sortby'];
  // Now to change the SQL query based on the sorting the user chose (price high to low, low to high, alphabetical and latest first)
  if ($sortby = 'pricehilo') {
    $sql = mysqli_query($con,"SELECT * FROM products ORDER BY price DESC");
  }
  elseif ($sortby = 'pricelohi') {
    $sql = mysqli_query($con,"SELECT * FROM products ORDER BY price ASC");
  }
  elseif ($sortby = 'name') {
    $sql = mysqli_query($con,"SELECT * FROM products ORDER BY product_name");
  }
}

该页面是index.php ，这些是HTML中的链接：

<p><a href="index.php?sortby=pricehilo">Price (Highest-Lowest)</a></p>
<p><a href="index.php?sortby=pricelohi">Price (Lowest-Highest)</a></p>
<p><a href="index.php?sortby=name">Alphabetical</a></p>

首次加载页面时，所有产品均按ID排序显示。 但是，当我单击任何链接时，产品将按照价格从高到低的顺序进行排序。 如果我仅按index.php刷新页面，则产品将按价格从高到低的顺序进行排序-所采用的SQL查询就是这样。

我怎样才能解决这个问题？

Answer 1

如果语句的内容=更改为==