How to: WordPress Count Words in a Post

Here is sample code I use to count words in a post ( I found it somewhere while searching something else). Put the code in functions.php (no need to write plugin)

function blog_post_wordcount() {
        global $page, $pages;
        if ( !function_exists('str_word_count') ) {
                return str_word_count(strip_tags($pages[$page-1]));
        } else {
                return count(explode(" ",strip_tags($pages[$page-1])));

You can call blog_post_wordcount() from template. Following code will display ad only if a post has more than 100 words:

if ( $words >= 100 ) { show_ad(): }