Automatically text replacement via WordPress function

Someday I will describe the way of creating a multisite for WordPress without database clones and installing plugins. But in this article I am describing a solution when several sites work with the same database and with the same admin panel, and for example, for a subdomain I need to automatically change the content (in this case, the city).

Copy and paste the function into functions.php as shown below:

$host = $_SERVER['HTTP_HOST']; 
if($host == "sub.domain.com" or $host == "www.sub.domain.com") {
	function replace_content($content) {
		$content = str_replace('first phrase to replace', 'edited first phrase',$content);
     		$content = str_replace('second phrase to replace', 'edited second phrase',$content);
     		$content = str_replace('third phrase to replace', 'edited third phrase',$content);
			return $content;
 		}
add_filter('the_content','replace_content');
}

Similarly, you can change the content on the fly depending on the language versions, when instead of checking the host, you can check the language prefix in the link.