WordPress at a glance
filter is not described

site_url filter-hook . WP 2.7.0

Filters the site URL.


add_filter( 'site_url', 'filter_function_name_5494', 10, 4 );
function filter_function_name_5494( $url, $path, $scheme, $blog_id ){
	// filter...

	return $url;
The complete site URL including scheme and path.
Path relative to the site URL. Blank string if no path is specified.
Scheme to give the site URL context. Accepts 'http', 'https', 'login', 'login_post', 'admin', 'relative' or null.
Site ID, or null for the current site.

Where the hook is called

wp-includes/link-template.php 3188
return apply_filters( 'site_url', $url, $path, $scheme, $blog_id );

Where the hook is used (in WP core)

Does not used.