目前，以下代码显示各个发行商的过滤器，即如果我选择DC，我将只看到DC标题。
问题是，从当前代码来看，我无法从下拉菜单中显示所有发布者。
<div id="main">
<form method="post" action="">
<div id="search_query" >
<select name="make" size="0">
<option value="all">All Publishers</option>
<option value="DC">DC</option>
<option value="Marvel">Marvel</option>
<option value="Image">Image</option>
</select>
<input type="submit" name="submit" value="submit">
</div>
</form>
<div id="main_container">
<?php
$db_con = mysql_connect('127.0.0.1','root','root');
if (!$db_con) {
die('Could not connect: ' . mysql_error());
}
mysql_select_db('work', $db_con);
if(isset($_POST['submit']))
{
$make = mysql_real_escape_string($_POST['make']);
$sql = sprintf("SELECT * FROM products WHERE publisher= '$make' ");
$result = mysql_query($sql);
echo "<table width= 970 border=1>
<tr>
<th width='120' scope='col'>Title</th>
<th width='170' scope='col'>Publisher</th>
<th width='185' scope='col'>Price</th>
<th width='126' scope='col'>Desc</th>
</tr>";
while($row = mysql_fetch_array($result))
{
echo "<tr>";
echo "<td>".$row['title']."</td>";
echo "<td>". $row['publisher'] . "</td>";
echo "<td>". $row['price'] ."</td>";
echo "<td>". $row['desc'] ."</td>";
echo "</tr>";
}
echo "</table>";
}
else
{
$sql = sprintf("SELECT * FROM products");
$result = mysql_query($sql);
echo "<table width= 970 border=1>
<tr>
<th width='120' scope='col'>Title</th>
<th width='170' scope='col'>Publisher</th>
<th width='185' scope='col'>Price</th>
<th width='126' scope='col'>Desc</th>
</tr>";
while($row = mysql_fetch_array($result))
{
echo "<tr>";
echo "<td>".$row['title']. "</td>";
echo "<td>". $row['publisher'] . "</td>";
echo "<td>". $row['price'] ."</td>";
echo "<td>". $row['desc'] ."</td>";
echo "</tr>";
}
echo "</table>";
}
mysql_close($db_con);
?>
在您的查询中，它正在搜索publisher=$make，其中$make="all"。您的数据库表可能没有任何publisher="make"的记录。
我建议你在这里添加一个if else条件：
if (isset($_POST['submit'])) {
$make = mysql_real_escape_string($_POST['make']);
if ($make != "all") {
$sql = sprintf("SELECT * FROM products WHERE publisher= '$make' ");
} else {
$sql = sprintf("SELECT * FROM products");
}
/* Other code */
}