How can PHP developers ensure that their forum posts are displayed correctly across different operating systems, such as Windows and Macintosh?

To ensure that forum posts are displayed correctly across different operating systems, PHP developers can use CSS to style the posts in a way that is compatible with various browsers and operating systems. By using CSS properties that are well-supported across different platforms, developers can ensure consistent display of forum posts.

<style>
    .forum-post {
        font-family: Arial, sans-serif;
        font-size: 14px;
        line-height: 1.5;
    }
</style>