Detailed explanation of the usage of wp_title() function in WordPress development, wordpresswp_title_PHP tutorial

/**
 * Display or retrieve page title for all areas of blog.
 *
 * By default, the page title will display the separator before the page title,
 * so that the blog title will be before the page title. This is not good for
 * title display, since the blog title shows up on most tabs and not what is
 * important, which is the page that the user is looking at.
 *
 * There are also SEO benefits to having the blog title after or to the 'right'
 * or the page title. However, it is mostly common sense to have the blog title
 * to the right with most browsers supporting tabs. You can achieve this by
 * using the seplocation parameter and setting the value to 'right'. This change
 * was introduced around 2.5.0, in case backwards compatibility of themes is
 * important.
 *
 * @since 1.0.0
 *
 * @param string $sep Optional, default is '»'. How to separate the various items within the page title.
 * @param bool $display Optional, default is true. Whether to display or retrieve title.
 * @param string $seplocation Optional. Direction to display title, 'right'.
 * @return string|null String on retrieve, null when displaying.
 */
function wp_title($sep = '»', $display = true, $seplocation = '') {
global $wpdb, $wp_locale;
 
$m = get_query_var('m');
$year = get_query_var('year');
$monthnum = get_query_var('monthnum');
$day = get_query_var('day');
$search = get_query_var('s');
$title = '';
 
$t_sep = '%WP_TITILE_SEP%'; // Temporary separator, for accurate flipping, if necessary
 
// If there is a post
if ( is_single() || ( is_home() && !is_front_page() ) || ( is_page() && !is_front_page() ) ) {
 $title = single_post_title( '', false );
}
 
// If there's a category or tag
if ( is_category() || is_tag() ) {
 $title = single_term_title( '', false );
}
 
// If there's a taxonomy
if ( is_tax() ) {
 $term = get_queried_object();
 $tax = get_taxonomy( $term->taxonomy );
 $title = single_term_title( $tax->labels->name . $t_sep, false );
}
 
// If there's an author
if ( is_author() ) {
 $author = get_queried_object();
 $title = $author->display_name;
}
 
// If there's a post type archive
if ( is_post_type_archive() )
 $title = post_type_archive_title( '', false );
 
// If there's a month
if ( is_archive() && !empty($m) ) {
 $my_year = substr($m, 0, 4);
 $my_month = $wp_locale->get_month(substr($m, 4, 2));
 $my_day = intval(substr($m, 6, 2));
 $title = $my_year . ( $my_month ? $t_sep . $my_month : '' ) . ( $my_day ? $t_sep . $my_day : '' );
}
 
// If there's a year
if ( is_archive() && !empty($year) ) {
 $title = $year;
 if ( !empty($monthnum) )
 $title .= $t_sep . $wp_locale->get_month($monthnum);
 if ( !empty($day) )
 $title .= $t_sep . zeroise($day, 2);
}
 
// If it's a search
if ( is_search() ) {
 /* translators: 1: separator, 2: search phrase */
$title = sprintf(__('Search Results %1$s %2$s'), $t_sep, strip_tags($search));
}
 
// If it's a 404 page
if ( is_404() ) {
 $title = __('Page not found');
}
 
$prefix = '';
if ( !empty($title) )
 $prefix = " $sep ";
 
// Determines position of the separator and direction of the breadcrumb
if ( 'right' == $seplocation ) { // sep on right, so reverse the order
$title_array = explode( $t_sep, $title );
$title_array = array_reverse( $title_array );
$title = implode( " $sep ", $title_array ) . $prefix;
} else {
 $title_array = explode( $t_sep, $title );
 $title = $prefix . implode( " $sep ", $title_array );
}
 
$title = apply_filters('wp_title', $title, $sep, $seplocation);
 
// Send it out
 if ( $display )
 echo $title;
 else
 return $title;
 
}

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