WORDPRESS: get excerpt outside loop

wp-excerpt-outside-loop.php

<?
/* works pretty well */
function the_excerpt_max_charlength($id=false, $charlength=55) {
	global $post;

	$old_post = $post;
	if ($id != $post->ID) {
		$post = get_page($id);
	}

	if (!$excerpt = trim($post->post_excerpt)) {
		//echo "<pre>" . print_r($post) . "</pre>";
		$excerpt = $post->post_content;
		$excerpt = strip_shortcodes( $excerpt );
		$excerpt = apply_filters('the_content', $excerpt);
		$excerpt = str_replace(']]>', ']]&gt;', $excerpt);
		$excerpt = strip_tags($excerpt);
		function set_new_excerpt_length($length) {
			return $charlength;
		}
		add_filter('excerpt_length', 'set_new_excerpt_length');
		$excerpt_length = apply_filters('excerpt_length', $charlength);

		$words = preg_split("/[\n\r\t ]+/", $excerpt, $excerpt_length + 1, PREG_SPLIT_NO_EMPTY);
		if ( count($words) > $excerpt_length ) {
			array_pop($words);
			$excerpt = implode(' ', $words);
			$excerpt = $excerpt . $excerpt_more;
		} else {
			$excerpt = implode(' ', $words);
		}
	}

	$post = $old_post;

	return $excerpt;
}