WordPress Function: Number of Words in Post Content

functions.php

function post_word_count() {
    $count = 0;
    $posts = get_posts( array(
        'numberposts' => -1,
        'post_type' => array( 'post', 'page' )
    ));
    foreach( $posts as $post ) {
        $count += str_word_count( strip_tags( get_post_field( 'post_content', $post->ID )));
    }
    $num =  number_format_i18n( $count );