strip tags on post save

function strip_tags_on_post_save($post_id)
{
    // If this is a revision, get real post ID
    if ($parent_id = wp_is_post_revision($post_id)) {
        $post_id = $parent_id;
    }

    // Get post content
    $post_object = get_post($post_id);

    // Check if this post has content
    if (!empty($post_object)) {
        // unhook this function so it doesn't loop infinitely
        remove_action('save_post', __NAMESPACE__ . '\\strip_tags_on_post_save');

        // Get just the post content
        $content = $post_object->post_content;

        // Keep just these tags
        $allowed_html = array(
            'a' => array(
                'href' => array(),
                'title' => array()
            ),
            'br' => array(),
            'em' => array(),
            'i' => array(),
            'strong' => array(),
            'b' => array(),
            'img' => array(),
            'ul' => array(),
            'ol' => array(),
            'li' => array(),
            'blockquote' => array(),
            'hr' => array(),
        );

        // Do it.
        $content_stripped = wp_kses($content, $allowed_html);

        // Update the post, which calls save_post again
        wp_update_post(array( 'ID' => $post_id, 'post_content' => $content_stripped ));
    }
}
add_action('save_post', __NAMESPACE__ . '\\strip_tags_on_post_save');