WordPress at a glance
function is not described

get_blog_option() WP 3.0.0

Retrieve option value for a given blog id based on name of option.

If the option does not exist or does not have a value, then the return value will be false. This is useful to check whether you need to install an option and is commonly used during installation of plugin options and to test whether upgrading is required.

If the option was serialized then it will be unserialized when it is returned.

Hooks from the function
Return

Mixed. Value set for the option.

Usage

get_blog_option( $id, $option, $default );
$id(int) (required)
A blog ID. Can be null to refer to the current blog.
$option(string) (required)
Name of option to retrieve. Expected to not be SQL-escaped.
$default(mixed)
Optional.
Default: value to return if the option does not exist

Changelog

Since 3.0.0 Introduced.

Code of get blog option: wp-includes/ms-blogs.php WP 5.2.3

<?php
function get_blog_option( $id, $option, $default = false ) {
	$id = (int) $id;

	if ( empty( $id ) ) {
		$id = get_current_blog_id();
	}

	if ( get_current_blog_id() == $id ) {
		return get_option( $option, $default );
	}

	switch_to_blog( $id );
	$value = get_option( $option, $default );
	restore_current_blog();

	/**
	 * Filters a blog option value.
	 *
	 * The dynamic portion of the hook name, `$option`, refers to the blog option name.
	 *
	 * @since 3.5.0
	 *
	 * @param string  $value The option value.
	 * @param int     $id    Blog ID.
	 */
	return apply_filters( "blog_option_{$option}", $value, $id );
}