twenty-fourteen 这个官网主题 function.php 里的代码:

body_class:
function twentyfourteen_body_classes( $classes ) {

    .....
    return $classes;
}
add_filter( 'body_class', 'twentyfourteen_body_classes' );
http://codex.WordPress.org/Function_Reference/body_class
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post_class:
function twentyfourteen_post_classes( $classes ) {
    if ( ! post_password_required() && ! is_attachment() && has_post_thumbnail() ) {
        $classes[] = 'has-post-thumbnail';
    }
    return $classes;
}
add_filter( 'post_class', 'twentyfourteen_post_classes' );
http://codex.WordPress.org/Function_Reference/post_class

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wp_title 是用于 seo 的
function twentyfourteen_wp_title( $title, $sep ) {
$sep 是可选 的
http://codex.WordPress.org/Function_Reference/wp_title