How do you post to the wall on a facebook page (not profile)

Get PHP SDK from github and run the following code:

<?php
$attachment = array(
    'message' => 'this is my message',
    'name' => 'This is my demo Facebook application!',
    'caption' => "Caption of the Post",
    'link' => 'http://mylink.com',
    'description' => 'this is a description',
    'picture' => 'http://mysite.com/pic.gif',
    'actions' => array(
        array(
            'name' => 'Get Search',
            'link' => 'http://www.google.com'
        )
    )
);

$result = $facebook->api('/me/feed/', 'post', $attachment);

the above code will Post the message on to your wall… and if you want to post onto your friends or others wall then replace me with the Facebook User Id of that user..for further information look out the API Documentation.