Source

File: wp-includes/ms-functions.php

function wpmu_create_blog( $domain, $path, $title, $user_id, $options = array(), $network_id = 1 ) {
	$defaults = array(
		'public' => 0,
	);
	$options  = wp_parse_args( $options, $defaults );

	$title   = strip_tags( $title );
	$user_id = (int) $user_id;

	// Check if the domain has been used already. We should return an error message.
	if ( domain_exists( $domain, $path, $network_id ) ) {
		return new WP_Error( 'blog_taken', __( 'Sorry, that site already exists!' ) );
	}

	if ( ! wp_installing() ) {
		wp_installing( true );
	}

	$allowed_data_fields = array( 'public', 'archived', 'mature', 'spam', 'deleted', 'lang_id' );

	$site_data = array_merge(
		array(
			'domain'     => $domain,
			'path'       => $path,
			'network_id' => $network_id,
		),
		array_intersect_key( $options, array_flip( $allowed_data_fields ) )
	);

	// Data to pass to wp_initialize_site().
	$site_initialization_data = array(
		'title'   => $title,
		'user_id' => $user_id,
		'options' => array_diff_key( $options, array_flip( $allowed_data_fields ) ),
	);

	$blog_id = wp_insert_site( array_merge( $site_data, $site_initialization_data ) );

	if ( is_wp_error( $blog_id ) ) {
		return $blog_id;
	}

	wp_cache_set( 'last_changed', microtime(), 'sites' );

	return $blog_id;
}