Force all posts to be assigned to a specific author on save

force-post-author.php

<?php
add_action( 'save_post', 'ba_force_post_author' );
function ba_force_post_author( $post_id ) {
	//verify post is not a revision
	if ( !wp_is_post_revision( $post_id ) ) {
		$mypost = array();
		$my_post['post_author'] = 2, //The user ID number of the author.
		$my_post['ID'] = $post_id;
		wp_update_post( $my_post );
	}
}