Restricting Content After the Tag

Using Simple Shortcode Conditionals

Intro content goes here--everyone will see this.

<!--more-->

[s2If current_user_can(access_s2member_level1)]
    Some content for Members who are logged in with an s2Member Level >= 1.
    [else]
        Some public content. You could put a notice here that says something like 
        "This content requires a membership. Please signup here (link)."
[/s2If]

Taking it A Step Further

Ninja Tip: Working example of programmatic protection of content below the  tag in WordPress.

Create this directory and file: /wp-content/mu-plugins/s2if-more-filter.php

<?php
function s2if_more_filter($content) {
    $members_only_message = "This content requires a membership. Please signup here (link).";
    $s2if_start = '[s2If !current_user_can(access_s2member_level1)]';
    $s2if_message = $members_only_message . ' [else]';
    $s2if_end = '[/s2If]';

    $pos1 = strpos($content, '<span id="more-');
    if($pos1 !== false) {
        $pos2 = strpos($content, '</span>', $pos1);
        $before_more_tag = substr($content, 0, $pos2);
        $after_more_tag = substr($content, $pos2);
        $content = $before_more_tag . $s2if_start . $s2if_message . $after_more_tag . $s2if_end;
    }

    return $content;
}
add_filter('the_content', 's2if_more_filter', 10, 1);