How do I get the content of an entire post besides the last line?

I have the following code to get the content of a post

<?php
$my_postid = $post->ID;
$content_post = get_post($my_postid);
$content = $content_post->post_content;
$content = apply_filters('the_content', $content);
$content = str_replace(']]>', ']]>', $content);
echo $content;
?>

How do I leave out the last line in that post?

Thanks!

[closed as duplicate – please post only one topic per problem; continue with http://wordpress.org/support/topic/how-do-i-get-the-content-of-an-entire-post-besides-the-last-line-1?replies=4 ]