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Editorial Team
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Asked: 2026-06-13T10:28:07+00:00

I’m trying to sort a PHP generated form by price. I get an error

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I’m trying to sort a PHP generated form by price. I get an error message ‘Notice: Undefined index: PriceDesc/Asc’. I understand the error message but can’t find any relevant info through searching so thought I’d ask. I’m new to PHP and so far this is the code I have:

<!DOCTYPE html>
<html lang="en">
 <head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <!--[if IE]>
  <link href="blueprint/ie.css" type="text/css" rel="stylesheet">
  <![endif]-->
  <link href="blueprint/screen.css" type="text/css" rel="stylesheet">
  <link href="style.css" type="text/css" rel="stylesheet">

  <title>Enygma Peripherals</title>
</head>

<body>
<div id="wrapper" class="container">
    <div id="top" class="span-24">
        <div id="logo" class="span-5">
            <a href="index.php"><img src="images/logo.png" alt="Enygma"></a>
        </div>
        <div id="nav" class="span-11 last">
            <ul>
                <li><a href="index.php">HOME</a></li>
                <li><a href="products.php">PRODUCTS</a></li>
                <li><a href="about.php">ABOUT</a></li>
                <li><a href="contact.php">CONTACT</a></li>
            </ul>
        </div>

    </div>
    <div id="mainContent" class="span-24">
        <h2>Products</h2>
        <div id="left" class="span-8">
        </div>
        <div id="right" class="span-15 last">
            <form method="get" name="sort">
                <select name="sort" id="sort">
                    <option value="">--Select--</option>
                    <option value='PriceAsc'>Price: Highest First</option>
                    <option value='PriceDesc'>Price: Lowest First</option> 
                </select>
                <input type="submit" value="Sort"/>
            </form>
            <?php
                include("connection.php");

                $data = mysql_query("SELECT * FROM products");
                IF ($_GET['PriceAsc']){
                    $orderby=" ORDER BY price ASC";
                } 
                IF ($_GET['PriceDesc']){
                    $orderby=" ORDER BY price DESC";
                }
                Print "<table border cellpadding=10>"; 
                while($info = mysql_fetch_array( $data )) 
                { 
                Print "<tr>"; 
                Print "<th>Product Number:</th> <td>".$info['product_no'] . "</td> "; 
                Print "<th>Product:</th> <td>".$info['product_name'] . "</td> "; 
                Print "<th>Type:</th> <td>".$info['type'] . "</td> "; 
                Print "<th>Price:</th> <td>".$info['price'] . "</td> "; 
                Print "<th>Availability:</th> <td>".$info['availability'] . " </td></tr>"; 
                } 
                Print "</table>"; 
                ?>
        </div>      
    </div>
    <div id="footer" class="span-24">
        <a href="acknowledgements.html">Acknowledgments</a>
    </div>
</div>

For the record, I’m using PhpMyAdmin for my backend d/b and the initial tabled data works fine.

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1 Answer

  1. Editorial Team

    Replace 

    $data = mysql_query("SELECT * FROM products");
            IF ($_GET['PriceAsc']){
                $orderby =" ORDER BY price ASC";
            } 
            IF ($_GET['PriceDesc']){
                $orderby =" ORDER BY price DESC";
            }

    with

    if ( !empty($_GET['sort']) && $_GET['sort'] == 'PriceAsc' ) {
    $orderby=" ORDER BY price ASC";
} 
if ( !empty($_GET['sort']) && $_GET['sort'] == 'PriceDesc' ) {
    $orderby=" ORDER BY price DESC";
}

$data = mysql_query("SELECT * FROM products".$orderby);

    Note the changes, you need to use empty() to check if form submitted and check the value of it. And do the query once Order by appended to SQL.

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