动态DropDownList工作，但如何获得价值？ PHP

Hi I have the following code:

$dropdown = "<select name='test'>";
while($row = mysql_fetch_assoc($result)) {
  $dropdown .= "
<option value='{$row['name']}'>{$row['name']}</option>";
}
$dropdown .= "
</select>";
echo $dropdown;


<form name="input" action="databaseupdate.php" method="post">
Select the car you want to edit and fill in the form, followed by clicking the update button.
<br>
Carname: <input type="text" name="nameupdate">
Year build: <input type="text" name="yearupdate">
<input type="submit" value="Update">
</form>

And this one (databaseupdate.php):

<?php
$username = "root";
$password = "usbw";
$hostname = "localhost"; 
$db_name = "examples"; 
$tbl_name = "cars"; 


mysql_connect("$hostname", "$username", "$password")or die("cannot connect"); 
mysql_select_db("$db_name")or die("cannot select DB");

$nameupdate = $_POST['nameupdate'];
$yearupdate = $_POST['yearupdate'];
$test = $_POST['test'];

$query = "UPDATE cars SET name = '$nameupdate', year = '$yearupdate' WHERE id='$test'"; 
mysql_query($query) or die (mysql_error()); 


if($query){
echo "Successful";
echo "<BR>";
echo "<a href='databaseconnect.php'>Back to main page</a>";
}

else {
echo "ERROR";
}
?>

So, the list is populated by all the car names from the database, which is good but from this point I don't know how to get the id that comes with the car's name.

I have tried it with a query that says "wher id='$test'" (as you can see in my code) but that returns empty.

Example of what I want:

If I select "Mercedes" from the dropdownlist and want to update it with the textboxes I want my code to know that Mercedes has an ID of 1.

I don't know how I can do that and I hope someone can help me out here.

Thanks.

do like this: (just add dropdown inside your form)

<?php
    $dropdown = "<select name='test'>";
    while($row = mysql_fetch_assoc($result)) {
      $dropdown .= "
<option value='{$row['id']}'>{$row['name']}</option>";
    }
    $dropdown .= "
</select>";
?>

    <form name="input" action="databaseupdate.php" method="post">
    Select the car you want to edit and fill in the form, followed by clicking the update button.
    <br>
    <?php echo $dropdown; ?>
    Carname: <input type="text" name="nameupdate">
    Year build: <input type="text" name="yearupdate">
    <input type="submit" value="Update">
    </form>

First of all include your dropdown inside the form.

Second if you want ID for your drop down selection, fetch id from db for the car name in $result, then do like this:

$dropdown = "<select name='test'>";
while($row = mysql_fetch_assoc($result)) {
$dropdown .= "
<option value='{$row['ID']}'>{$row['name']}</option>";
}
$dropdown .= "
</select>";

<form name="input" action="databaseupdate.php" method="post">
Select the car you want to edit and fill in the form, followed by clicking the update button.
 <br>
echo $dropdown;
Carname: <input type="text" name="nameupdate">
Year build: <input type="text" name="yearupdate">
<input type="submit" value="Update">
</form>

Done.

<form name="input" action="databaseupdate.php" method="post">
Select the car you want to edit and fill in the form, followed by clicking the update     button.
<br>
Carname: <input type="text" name="nameupdate">
Year build: <input type="text" name="yearupdate">
<select name='test'>
<?php while($row = mysql_fetch_assoc($result)) {
  echo "
<option value='{$row['name']}'>{$row['name']}</option>";
}?>
</select>
<input type="submit" value="Update">
</form>

in your databaseupdate.php

$values = $_POST['test'];

$values contains selected values

The main problem is that you didn't included your select into form tag. Also to get values from POST method you should use $_POST in PHP or $_REQUEST

to check what $_POST contains you can use function

var_dump($_POST);