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/*
 *  Filter to display a Font Awesome Padlock Icon next to the post title of restricted content for WooCommerce Memberships.
 */
function wcm_add_icon_next_to_restricted_post( $post_title, $post_id ) {
    if ( is_admin() ) {
        return;
    }

    if ( wc_memberships_is_post_content_restricted( $post_id ) ) {
        return '<i class="fa fa-lock" aria-hidden="true"></i>' . '&nbsp;' . $post_title;
    }

    return $post_title;
}
add_filter( 'the_title', 'wcm_add_icon_next_to_restricted_post', 10, 2 );