signup_another_blog( string $blogname = '', string $blog_title = '', WP_Error|string $errors = '' )

function signup_another_blog( $blogname = '', $blog_title = '', $errors = '' ) {
	$current_user = wp_get_current_user();

	if ( ! is_wp_error($errors) ) {
		$errors = new WP_Error();
	}

	$signup_defaults = array(
		'blogname'   => $blogname,
		'blog_title' => $blog_title,
		'errors'     => $errors
	);

	/**
	 * Filters the default site sign-up variables.
	 *
	 * @since WP-3.0.0
	 *
	 * @param array $signup_defaults {
	 *     An array of default site sign-up variables.
	 *
	 *     @type string   $blogname   The site blogname.
	 *     @type string   $blog_title The site title.
	 *     @type WP_Error $errors     A WP_Error object possibly containing 'blogname' or 'blog_title' errors.
	 * }
	 */
	$filtered_results = apply_filters( 'signup_another_blog_init', $signup_defaults );

	$blogname = $filtered_results['blogname'];
	$blog_title = $filtered_results['blog_title'];
	$errors = $filtered_results['errors'];

	echo '<h2>' . sprintf( __( 'Get <em>another</em> %s site in seconds' ), get_network()->site_name ) . '</h2>';

	if ( $errors->get_error_code() ) {
		echo '<p>' . __( 'There was a problem, please correct the form below and try again.' ) . '</p>';
	}
	?>
	<p><?php printf( __( 'Welcome back, %s. By filling out the form below, you can <strong>add another site to your account</strong>. There is no limit to the number of sites you can have, so create to your heart&#8217;s content, but write responsibly!' ), $current_user->display_name ) ?></p>

	<?php
	$blogs = get_blogs_of_user($current_user->ID);
	if ( !empty($blogs) ) { ?>

			<p><?php _e( 'Sites you are already a member of:' ) ?></p>
			<ul>
				<?php foreach ( $blogs as $blog ) {
					$home_url = get_home_url( $blog->userblog_id );
					echo '<li><a href="' . esc_url( $home_url ) . '">' . $home_url . '</a></li>';
				} ?>
			</ul>
	<?php } ?>

	<p><?php _e( 'If you&#8217;re not going to use a great site domain, leave it for a new user. Now have at it!' ) ?></p>
	<form id="setupform" method="post" action="wp-signup.php">
		<input type="hidden" name="stage" value="gimmeanotherblog" />
		<?php
		/**
		 * Hidden sign-up form fields output when creating another site or user.
		 *
		 * @since WP-MU (3.0.0)
		 *
		 * @param string $context A string describing the steps of the sign-up process. The value can be
		 *                        'create-another-site', 'validate-user', or 'validate-site'.
		 */
		do_action( 'signup_hidden_fields', 'create-another-site' );
		?>
		<?php show_blog_form($blogname, $blog_title, $errors); ?>
		<p class="submit"><input type="submit" name="submit" class="submit" value="<?php esc_attr_e( 'Create Site' ) ?>" /></p>
	</form>
	<?php
}