从Double下拉菜单中选择PHP中的值

Question

I am creating a drop-down menu in which the second drop-down is dependent upon the first; the first drop down is a list of table, and depending on what table you select, the columns of that table will be able to be selected.

<form id = "table_column" action = "file_name.php">
    <select id = "tables" name = "tables" onclick = "script();">
        <option name = "table_option_one" value = "people">people</option>
        <option>...</option>
    </select>
    <select id = "columns" name = "columns" onclick = "other_script();">
        <option name = "column_option_one" value = "name">name</option>
        <option>...</option>
    </select>
    <input type = "submit"></input>
</form>

I have tried the code below to no success.

$table_name = $_POST["tables"];
$column_name = $_POST["columns"];

How do I access the values selected in each drop-down menu in PHP?

I am only having a problem with the retrieval of the selected values. The menus depending on another and switching work fine

Answer 1

Okay, with your new clarification (you are populating the drop-downs fine), here is what you can do.

Give the input tag an ID as such:

<input type="submit" name="submit" id="submit" value="Submit"> <!--form submit button-->

and in your PHP do a conditional as such:

if (isset($_POST['submit'])) {
    $table_name = $_POST["tables"];
    $column_name = $_POST["columns"];
}

make sure your form also has the method="post" attribute as well:

<form id = "table_column" action="file_name.php" method="post">

That way when the submit button is hit, your values will be retrieved.