使用get_user_by 和get_term_by 功能：

// user
$user = get_user_by( \'login\', \'someuser\' );
if( $user ){
    echo get_author_posts_url( $user->ID );
}

// tag
$term = get_term_by( \'name\', \'Sometag\', \'post_tag\' );
if( $term ){
    echo get_term_link( $term );
}