validate_blog_signup()

function validate_blog_signup() {
	// Re-validate user info.
	$user_result = wpmu_validate_user_signup( $_POST['user_name'], $_POST['user_email'] );
	$user_name = $user_result['user_name'];
	$user_email = $user_result['user_email'];
	$user_errors = $user_result['errors'];

	if ( $user_errors->get_error_code() ) {
		signup_user( $user_name, $user_email, $user_errors );
		return false;
	}

	$result = wpmu_validate_blog_signup( $_POST['blogname'], $_POST['blog_title'] );
	$domain = $result['domain'];
	$path = $result['path'];
	$blogname = $result['blogname'];
	$blog_title = $result['blog_title'];
	$errors = $result['errors'];

	if ( $errors->get_error_code() ) {
		signup_blog($user_name, $user_email, $blogname, $blog_title, $errors);
		return false;
	}

	$public = (int) $_POST['blog_public'];
	$signup_meta = array ('lang_id' => 1, 'public' => $public);

	// Handle the language setting for the new site.
	if ( ! empty( $_POST['WPLANG'] ) ) {

		$languages = signup_get_available_languages();

		if ( in_array( $_POST['WPLANG'], $languages ) ) {
			$language = wp_unslash( sanitize_text_field( $_POST['WPLANG'] ) );

			if ( $language ) {
				$signup_meta['WPLANG'] = $language;
			}
		}

	}

	/** This filter is documented in wp-signup.php */
	$meta = apply_filters( 'add_signup_meta', $signup_meta );

	wpmu_signup_blog($domain, $path, $blog_title, $user_name, $user_email, $meta);
	confirm_blog_signup($domain, $path, $blog_title, $user_name, $user_email, $meta);
	return true;
}