Hello @kartik,
Sending an HTTP POST request using file_get_contents is not that hard, actually : as you guessed, you have to use the $context parameter.
Example  :
$postdata = http_build_query(
    array(
        'var1' => 'some content',
        'var2' => 'doh'
    )
);
$opts = array('http' =>
    array(
        'method'  => 'POST',
        'header'  => 'Content-Type: application/x-www-form-urlencoded',
        'content' => $postdata
    )
);
$context  = stream_context_create($opts);
$result = file_get_contents('http://example.com/submit.php', false, $context);
Basically, you have to create a stream, with the right options (there is a full list on that page), and use it as the third parameter to file_get_contents .
Hope it helps!!
Thank You!!