Automatically Add Dynamic Title to Pages in WordPress

functions.php

<?php 
/* Dynamic Titles **/
// This sets your <title> depending on what page you're on, for better formatting and for SEO
// You need to set the variable $longd to some custom text at the beginning of the function
function dynamictitles() {
    $longd = __('Enter your longdescription here.', 'texdomainstring');
    if ( is_single() ) {
        wp_title('');
        echo ' | '.get_bloginfo('name');
    } else if ( is_page() || is_paged() ) {
        bloginfo('name');
        wp_title('|');
    } else if ( is_author() ) {
        bloginfo('name');
        wp_title(' | '.__('Author', 'texdomainstring'));
    } else if ( is_category() ) {
        bloginfo('name');
        wp_title(' | '.__('Archive for', 'texdomainstring'));
    } else if ( is_tag() ) {
        echo get_bloginfo('name').' | '.__('Tag archive for', 'texdomainstring');
        wp_title('');
    } else if ( is_archive() ) {
        echo get_bloginfo('name').' | '.__('Archive for', 'texdomainstring');
        wp_title('');
    } else if ( is_search() ) {
        echo get_bloginfo('name').' | '.__('Search Results', 'texdomainstring');
    } else if ( is_404() ) {
        echo get_bloginfo('name').' | '.__('404 Error (Page Not Found)', 'texdomainstring');
    } else if ( is_home() ) {
        echo get_bloginfo('name').' | '.get_bloginfo('description');
    } else {
        echo get_bloginfo('name').' | '.($blog_longd);
    }
}