yes i have copied everything and trying to understand it.
<?php
$parameterString = 'POST&https%3A%2F%2Fapi.twitter.com%2F1%2Fstatuses%2Fupdate.json&include_entities%3Dtrue%26oauth_consumer_key%3Dxvz1evFS4wEEPTGEFPHBog%26oauth_nonce%3DkYjzVBB8Y0ZFabxSWbWovY3uYSQ2pTgmZeNu2VS4cg%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp%3D1318622958%26oauth_token%3D370773112-GmHxMAgYyLbNEtIKZeRNFsMKPR9EyMZeS9weJAEb%26oauth_version%3D1.0%26status%3DHello%2520Ladies%2520%252B%2520Gentlemen%252C%2520a%2520signed%2520OAuth%2520request%2521';
$secret = 'kAcSOqF21Fu85e7zjz7ZN2U4ZRhfV3WpwPAoE3Z7kBw&LswwdoUaIvS8ltyTt5jkRh4J50vUPVVHtR2YPi5kE';
$key = hash_hmac('sha1',$parameterString,$secret);
echo $key.'<br/><br/>';
$key = strtoupper($key);
echo $key.'<br/><br/>';
echo base64_encode($key).'<br/><br/>';
?></code>
and the echo is:
b679c0af18f4e9c587ab8e200acd4e48a93f8cb6
B679C0AF18F4E9C587AB8E200ACD4E48A93F8CB6
QjY3OUMwQUYxOEY0RTlDNTg3QUI4RTIwMEFDRDRFNDhBOTNGOENCNg==