Source

File: wp-includes/option.php

function set_user_setting( $name, $value ) {
	if ( headers_sent() ) {
		return false;
	}

	$all_user_settings          = get_all_user_settings();
	$all_user_settings[ $name ] = $value;

	return wp_set_all_user_settings( $all_user_settings );
}