Form display after submission - forms

Question

I am trying to build a simple CMS and have run into a problem I hope you can help me with.
I have a public display page that fetches data from a MySQL database. This works fine.
I also have an admin page where the data is loaded into a form field so that a maintainer can change it.
My problem is that after hitting the submit button, the data is successfully sent to the DB but I cannot find a way to get the form to show the latest data. It is always one submit step behind.
Sample code:
<?php
//retrieve data from MySQL
mysql_connect('localhost:3306','dundryor_show','show1');
mysql_select_db('dundryor_stofl_test');
$query = mysql_query("SELECT * FROM form_test where id = '0'");
$output = mysql_fetch_array($query);
$user_text = $output['user_text'];
mysql_close();
//display form and populate
echo '<form method="post">';
echo 'This text is stored in the database and can be changed by the user:<p>';
echo '<input type="Text" name="user_text" size="50" value="';
echo $user_text;
echo '"><br><input type="Submit" name="update" value="Update Database">';
echo '</form>';
//process submit event, write new data to DB
if ($_POST['update'])
{
$user_text = $_POST['user_text'];
mysql_connect('localhost:3306','dundryor_show','show1');
mysql_select_db('dundryor_stofl_test');
mysql_query("UPDATE form_test set user_text = '$user_text' where id = '0'");
mysql_close();
}
?>
As an added complication, the file name needs to be dynamic, i.e. not just "myform.php" but "myform.php?option=this_can_be_anything". So a reference to a static URL would not work.
Any suggestions much appreciated.