bp_core_signup_user( string $user_login, string $user_password, string $user_email, array $usermeta )

function bp_core_signup_user( $user_login, $user_password, $user_email, $usermeta ) {
	$bp = buddypress();

	// We need to cast $user_id to pass to the filters.
	$user_id = false;

	// Multisite installs have their own install procedure.
	if ( is_multisite() ) {
		wpmu_signup_user( $user_login, $user_email, $usermeta );

	} else {
		// Format data.
		$user_login     = preg_replace( '/\s+/', '', sanitize_user( $user_login, true ) );
		$user_email     = sanitize_email( $user_email );
		$activation_key = wp_generate_password( 32, false );

		/**
		 * WordPress's default behavior is to create user accounts
		 * immediately at registration time. BuddyPress uses a system
		 * borrowed from WordPress Multisite, where signups are stored
		 * separately and accounts are only created at the time of
		 * activation. For backward compatibility with plugins that may
		 * be anticipating WP's default behavior, BP silently creates
		 * accounts for registrations (though it does not use them). If
		 * you know that you are not running any plugins dependent on
		 * these pending accounts, you may want to save a little DB
		 * clutter by defining setting the BP_SIGNUPS_SKIP_USER_CREATION
		 * to true in your wp-config.php file.
		 */
		if ( ! defined( 'BP_SIGNUPS_SKIP_USER_CREATION' ) || ! BP_SIGNUPS_SKIP_USER_CREATION ) {
			$user_id = BP_Signup::add_backcompat( $user_login, $user_password, $user_email, $usermeta );

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

			bp_update_user_meta( $user_id, 'activation_key', $activation_key );
		}

		$args = array(
			'user_login'     => $user_login,
			'user_email'     => $user_email,
			'activation_key' => $activation_key,
			'meta'           => $usermeta,
		);

		BP_Signup::add( $args );

		/**
		 * Filters if BuddyPress should send an activation key for a new signup.
		 *
		 * @since BuddyPress 1.2.3
		 *
		 * @param bool   $value          Whether or not to send the activation key.
		 * @param int    $user_id        User ID to send activation key to.
		 * @param string $user_email     User email to send activation key to.
		 * @param string $activation_key Activation key to be sent.
		 * @param array  $usermeta       Miscellaneous metadata about the user (blog-specific
		 *                               signup data, xprofile data, etc).
		 */
		if ( apply_filters( 'bp_core_signup_send_activation_key', true, $user_id, $user_email, $activation_key, $usermeta ) ) {
			bp_core_signup_send_validation_email( $user_id, $user_email, $activation_key, $user_login );
		}
	}

	$bp->signup->username = $user_login;

	/**
	 * Fires at the end of the process to sign up a user.
	 *
	 * @since BuddyPress 1.2.2
	 *
	 * @param bool|WP_Error   $user_id       True on success, WP_Error on failure.
	 * @param string          $user_login    Login name requested by the user.
	 * @param string          $user_password Password requested by the user.
	 * @param string          $user_email    Email address requested by the user.
	 * @param array           $usermeta      Miscellaneous metadata about the user (blog-specific
	 *                                       signup data, xprofile data, etc).
	 */
	do_action( 'bp_core_signup_user', $user_id, $user_login, $user_password, $user_email, $usermeta );

	return $user_id;
}