PHP var_dump只输出底部复选框的值

Hi and thanks for reading my question. I am using a simple form to get some input :

<p>Select your favorite two countries below:</p>

<form id="world" name="world" action="/order.php" method="post">
<input type="checkbox" name="countries" value="USA" /> USA<br />
<input type="checkbox" name="countries" value="Canada" /> Canada<br />
<input type="checkbox" name="countries" value="Japan" /> Japan<br />
<input type="checkbox" name="countries" value="China" /> China<br />
<input type="checkbox" name="countries" value="France" /> France<br />
<input type="submit" value="Order">
</form>

I want to make sure order.php is geting all of the choices selected, so order.php only contains the following code :

<pre>
<?php var_dump($_POST);?>
</pre>

Unfortunately, it is only outputting whatevre is the bottom-most checkbox that is checked.

The output is like this :

array(1) { ["countries"]=> string(6) "Canada" }

If i try the following code for output :

<?php
    foreach($_POST as $key=>$post_data){
        echo "You posted:" . $key . " = " . $post_data . "<br>";
    }
?>

I get this output :

You posted:countries = Canada

Can anyone tell me where i am going wrong and how i can retrieve all of the data, for every box that is ticked ?

Thank you.

<p>Select your favorite two countries below:</p>

<form id="world" name="world" action="/order.php" method="post">
<input type="checkbox" name="countries[]" value="USA" /> USA<br />
<input type="checkbox" name="countries[]" value="Canada" /> Canada<br />
<input type="checkbox" name="countries[]" value="Japan" /> Japan<br />
<input type="checkbox" name="countries[]" value="China" /> China<br />
<input type="checkbox" name="countries[]" value="France" /> France<br />
<input type="submit" value="Order">
</form>

Change it to above, this will store all your checkboxes results for you!

You gave the same name to your checkboxes, and PHP will overwrite previously parsed name submissions with the current value. You need to use the array-notation hack:

<input type="checkbox" name="countries[]" value="Canada" /> Canada<br />
                                      ^^

which then makes $_POST['countries'] an array of all the values submitted.

echo "You posted: " . implode(',', $_POST['countries']);