WPC — Add site title to every post title.

wpc-functions.php

<?php
/**
 * Add Site Title.
 *
 * Add site title to every post title.
 * 
 * @param string $title - Title of the post.
 */
function wpc_add_sitename_to_title( $title ) {
	// Get the site title.
	$site_name = get_bloginfo( 'name' );
	
	// Concatenate the site name to the post title.
	$title = $site_name . ' — ' . $title;
	
	// Return the modified title.
	return $title;	 	 
}

// Hook it!
add_filter( 'the_title', 'wpc_add_sitename_to_title', 10, 1 );