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filter is not described

http_request_host_is_external filter-hook . WP 3.6.0

Check if HTTP request is external or not.

Allows to change and allow external requests for the HTTP request.

Usage

add_filter( 'http_request_host_is_external', 'filter_function_name_306', 10, 3 );
function filter_function_name_306( $false, $host, $url ){
	// filter...

	return $false;
}
$false(true/false)
false Whether HTTP request is external or not.
$host(string)
IP of the requested host.
$url(string)
URL of the requested host.

Where the hook is called

wp_http_validate_url()
http_request_host_is_external
wp-includes/http.php 565
if ( ! apply_filters( 'http_request_host_is_external', false, $host, $url ) )

Where the hook is used (in WP core)

wp-includes/ms-default-filters.php 100
add_filter( 'http_request_host_is_external', 'ms_allowed_http_request_hosts', 20, 2 );
wp-includes/default-filters.php 254
add_filter( 'http_request_host_is_external', 'allowed_http_request_hosts', 10, 2 );