validate_user_signup

function validate_user_signup() {
	$result     = validate_user_form();
	$user_name  = $result['user_name'];
	$user_email = $result['user_email'];
	$errors     = $result['errors'];

	if ( $errors->has_errors() ) {
		signup_user( $user_name, $user_email, $errors );
		return false;
	}

	if ( 'blog' === $_POST['signup_for'] ) {
		signup_blog( $user_name, $user_email );
		return false;
	}

	/** This filter is documented in wp-signup.php */
	wpmu_signup_user( $user_name, $user_email, apply_filters( 'add_signup_meta', array() ) );

	confirm_user_signup( $user_name, $user_email );
	return true;
}