WordPress at a glance
filter is not described

pre_get_site_by_path filter-hook . WP 3.9.0

Determine a site by its domain and path.

This allows one to short-circuit the default logic, perhaps by replacing it with a routine that is more optimal for your setup.

Return null to avoid the short-circuit. Return false if no site can be found at the requested domain and path. Otherwise, return a site object.

Usage

add_filter( 'pre_get_site_by_path', 'filter_function_name_6401', 10, 5 );
function filter_function_name_6401( $site, $domain, $path, $segments, $paths ){
	// filter...

	return $site;
}
$site(null/true/false/WP_Site)
Site value to return by path.
$domain(string)
The requested domain.
$path(string)
The requested path, in full.
$segments(int/null)
The suggested number of paths to consult.
Default: null, meaning the entire path was to be consulted
$paths(array)
The paths to search for, based on $path and $segments.

Where the hook is called

get_site_by_path()
wp-includes/ms-load.php 204
$pre = apply_filters( 'pre_get_site_by_path', null, $domain, $path, $segments, $paths );

Where the hook is used (in WP core)

Does not used.