php - How do I obtain the value of the option that was chosen in a select from?

In the PHP code below I have created a form that is used to create a drop down list.

echo "";
echo "
";
echo "
 Agency Network 
";
echo "
";
echo "";
while($result1 = mysqli_fetch_assoc($result)) {
    unset($network_id, $network_name);
    $network_id = $network_name['network_id'];
    $network_name = $result1['network_code'];

    echo '' . $network_name . '';
    $network_chosen = $network_id;

}

echo "";
echo "";
echo "
";
echo "
";
?>

This code works as desired. It populates a drop down list based on the results of a database query. After the form has been submitted, I want to obtain the option that was selected and use it in another query. After the submit, I print the contents of the $_POST variable using:

print_r($_POST);

and my results are as follow:
Array ( [network] => [submit] => Send )

I want to get the value that was selected for network but it appears to be blank. Can anyone tell me what I'm doing wrong.

By the way, I am really new at coding and this is my first time using SO so please excuse any usage errors on my part. Thanks.