automatically form submission with webbot

Hi everyone
i am reading "Webbots, Spiders, and Screen Scrapers" book and
i want to create a webbot that automatically submit a form ,
but it has no out put.
this is the code :

<?php
include("LIB_http.php");

# Initiate addresses
$action="http://ce.usc.ac.ir/courses/86-87/sem2/112079/912/index.php?section=users&amp;file=sign&amp;id=in";
$ref = "" ;

# Set submission method
$method="POST";

# Set form data and values
$data_array['username'] = "83111207"; // my user name
$data_array['password'] = "83111207"; // my pass
$response = http($target=$action, $ref, $method, $data_array, EXCL_HEAD);
?>

PHP:

and http://ce.usc.ac.ir/courses/86-87/sem2/112079/912/
is address of the form.
you can get LIB_http.php from https://panel.schrenk.com

thank you in advance

 

echo $response;

PHP:

 

Thank you very much!
just the action must be : http://ce.usc.ac.ir/courses/86-87/sem2/112079/912/index.php