The myfnc() exists on the server-side and is to be executed on the server-side only, it will not appear on the client-side, you have to submit the form to the server and call the function over there, try this:
<form action="trytocallfunction.php" method="post">
<input type="submit" name="submit" value="submit">
</form>
You should read this to find out more
Beginner's Guide to HTML5 & CSS3 - Server Side Story[
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