从下拉菜单中选择未插入到已分配的变量[关闭]

I have used nearly this exact code on another page and it worked great, but here... not so much.

I have a drop down menu populated with elements from database columns. Whichever element is selected should be stored in the variable $Product, but for some reason I cannot figure out, it is simply not making it there and the rest of my script (parts I didn't post) doesn't work. Thanks in advance for your help.

<?php
    if(isset($_POST['submit'])) {
        $Product = $_POST['Product_List'];
    } else {
        $Product = "";
    }
?>
<!DOCTYPE html>
<html>
    <head>
        <title>Add Chemical Inventory</title>
    </head>
    <body>
        <div id="form_div">
            <div id="form_label">
                <h2>Add Chemical Inventory</h2>
                <form action="Add_Chemical_Inventory.php">
                    <?php
                    $List = "SELECT Product_ID, Product_Name FROM `products`";
                    $list_result = mysqli_query($connection,$List); 
                    echo "Product: <select name='Product_List'>";
                    while($row = mysqli_fetch_assoc($list_result)){
                        echo "<option value='".$row['Product_ID'] ."'>".$row['Product_Name']."</option>";
                    }
                    echo "</select>";
                    echo "<br />";
                    ?>
                </form>
            </div>
        </div>
    </body>
</html>

You forgot the method attribute on your <form> tag.

Thing is, by default, the method is set to get, and since your code expects post data, it just doesn't save it to the variable.

<form action="Add_Chemical_Inventory.php" method="post"></form>