How to add a post class on every post. (on homepage)

Question

I have this code in my home.php, the very first post class does not get the class while the others do. Same thing when i move this code to functions.php. I get php errors when i remove the hook around it and just add the filter.

add_action('pre_get_posts', 'theme_add_post_class');

function theme_add_post_class() {

    /** Add custom post class */
    add_filter( 'post_class', function( $classes ) {
        $classes[] = 'span4';
        return $classes;
    } );

}

}

Answer 1

function wpse80148_filter_post_class( $classes ) {
    if( is_home() || is_front_page() )
        $classes[] = 'span4';
    return $classes;
}
add_filter( 'post_class', 'wpse80148_filter_post_class' );