how to write javascript code inside php

Question

i have a got a form, on clicking the submit button:

1. I want to do some task in the same file (db task) AND
2. I want the form data to be sent to test.php with the redirection

here is my code

    <?php
    if(isset($_POST['btn'])){
        //do some task
    ?>
    <script type="text/javascript">
        var e = document.getElementById('testForm'); e.action='test.php'; e.submit();</script>
    <?php
    }
    ?>
<form name="testForm" id="testForm"  method="POST"  >
    <input type="submit" name="btn" value="submit" autofocus  onclick="return true;"/>
 </form>

but not able to submit the form, if i call the javascript code on onClick, it works.what is the problem in this code, Is there any work around for this

question from:https://stackoverflow.com/questions/10596218/how-to-write-javascript-code-inside-php