curl() on PHP.

I would like learn about curl() on PHP.
I have downloaded many codes to get address books from gmail,yahoo, etc
But I have sufficient knowledge on that topic.
So I want to know the answers for these questions
Can I use this curl for access any sites which contains login forms?
How can I do this?

Hi I have learned a bit about it.
My testing target is http://sms.wow.lk
This site can send a sms to our phones.(Only for my country)

So I wrote code like this

PHP Code:

---



<?php $page = '';
$cookie_jar = tempnam('/tmp','cookie');

// for logon into site
$c = curl_init('http://sms.wow.lk/user/login.php');
curl_setopt($c, CURLOPT_POST, 1);
curl_setopt($c, CURLOPT_POSTFIELDS, 'Username=vbforums&Password=test&Action=login');
curl_setopt($c, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($c, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($c, CURLOPT_COOKIEJAR, $cookie_jar);

curl_exec($c);
curl_close($c);

//Send SMS
$c = curl_init('http://sms.wow.lk/user/sendmessages.php');
curl_setopt($c, CURLOPT_POST, 1);
curl_setopt($c, CURLOPT_POSTFIELDS, 'message=Test123&sizebox=6&Action=send&1054427=checkbox');
curl_setopt($c, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($c, CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($c, CURLOPT_COOKIEJAR, $cookie_jar);

$page = curl_exec($c);
curl_close($c);

// remove the cookie jar
unlink($cookie_jar) or die("Can't unlink $cookie_jar");

echo $page;


?>

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But I can login sucessfully and but I can't able to send SMS.
What is the problem on my code?