function edit_user( $user_id = 0 ) {
	$wp_roles = wp_roles();
	$user     = new stdClass;
	$user_id  = (int) $user_id;
	if ( $user_id ) {
		$update           = true;
		$user->ID         = $user_id;
		$userdata         = get_userdata( $user_id );
		$user->user_login = wp_slash( $userdata->user_login );
	} else {
		$update = false;
	}

	if ( ! $update && isset( $_POST['user_login'] ) ) {
		$user->user_login = sanitize_user( $_POST['user_login'], true );
	}

	$pass1 = $pass2 = '';
	if ( isset( $_POST['pass1'] ) ) {
		$pass1 = $_POST['pass1'];
	}
	if ( isset( $_POST['pass2'] ) ) {
		$pass2 = $_POST['pass2'];
	}

	if ( isset( $_POST['role'] ) && current_user_can( 'promote_users' ) && ( ! $user_id || current_user_can( 'promote_user', $user_id ) ) ) {
		$new_role = sanitize_text_field( $_POST['role'] );

		// If the new role isn't editable by the logged-in user die with error.
		$editable_roles = get_editable_roles();
		if ( ! empty( $new_role ) && empty( $editable_roles[ $new_role ] ) ) {
			wp_die( __( 'Sorry, you are not allowed to give users that role.' ), 403 );
		}

		$potential_role = isset( $wp_roles->role_objects[ $new_role ] ) ? $wp_roles->role_objects[ $new_role ] : false;

		/*
		 * Don't let anyone with 'promote_users' edit their own role to something without it.
		 * Multisite super admins can freely edit their roles, they possess all caps.
		 */
		if (
			( is_multisite() && current_user_can( 'manage_network_users' ) ) ||
			$user_id !== get_current_user_id() ||
			( $potential_role && $potential_role->has_cap( 'promote_users' ) )
		) {
			$user->role = $new_role;
		}
	}

	if ( isset( $_POST['email'] ) ) {
		$user->user_email = sanitize_text_field( wp_unslash( $_POST['email'] ) );
	}
	if ( isset( $_POST['url'] ) ) {
		if ( empty( $_POST['url'] ) || $_POST['url'] == 'http://' ) {
			$user->user_url = '';
		} else {
			$user->user_url = esc_url_raw( $_POST['url'] );
			$protocols      = implode( '|', array_map( 'preg_quote', wp_allowed_protocols() ) );
			$user->user_url = preg_match( '/^(' . $protocols . '):/is', $user->user_url ) ? $user->user_url : 'http://' . $user->user_url;
		}
	}
	if ( isset( $_POST['first_name'] ) ) {
		$user->first_name = sanitize_text_field( $_POST['first_name'] );
	}
	if ( isset( $_POST['last_name'] ) ) {
		$user->last_name = sanitize_text_field( $_POST['last_name'] );
	}
	if ( isset( $_POST['nickname'] ) ) {
		$user->nickname = sanitize_text_field( $_POST['nickname'] );
	}
	if ( isset( $_POST['display_name'] ) ) {
		$user->display_name = sanitize_text_field( $_POST['display_name'] );
	}

	if ( isset( $_POST['description'] ) ) {
		$user->description = trim( $_POST['description'] );
	}

	foreach ( wp_get_user_contact_methods( $user ) as $method => $name ) {
		if ( isset( $_POST[ $method ] ) ) {
			$user->$method = sanitize_text_field( $_POST[ $method ] );
		}
	}

	if ( $update ) {
		$user->rich_editing         = isset( $_POST['rich_editing'] ) && 'false' === $_POST['rich_editing'] ? 'false' : 'true';
		$user->syntax_highlighting  = isset( $_POST['syntax_highlighting'] ) && 'false' === $_POST['syntax_highlighting'] ? 'false' : 'true';
		$user->admin_color          = isset( $_POST['admin_color'] ) ? sanitize_text_field( $_POST['admin_color'] ) : 'fresh';
		$user->show_admin_bar_front = isset( $_POST['admin_bar_front'] ) ? 'true' : 'false';
		$user->locale               = '';

		if ( isset( $_POST['locale'] ) ) {
			$locale = sanitize_text_field( $_POST['locale'] );
			if ( 'site-default' === $locale ) {
				$locale = '';
			} elseif ( '' === $locale ) {
				$locale = 'en_US';
			} elseif ( ! in_array( $locale, get_available_languages(), true ) ) {
				$locale = '';
			}

			$user->locale = $locale;
		}
	}

	$user->comment_shortcuts = isset( $_POST['comment_shortcuts'] ) && 'true' == $_POST['comment_shortcuts'] ? 'true' : '';

	$user->use_ssl = 0;
	if ( ! empty( $_POST['use_ssl'] ) ) {
		$user->use_ssl = 1;
	}

	$errors = new WP_Error();

	/* checking that username has been typed */
	if ( $user->user_login == '' ) {
		$errors->add( 'user_login', __( '<strong>ERROR</strong>: Please enter a username.' ) );
	}

	/* checking that nickname has been typed */
	if ( $update && empty( $user->nickname ) ) {
		$errors->add( 'nickname', __( '<strong>ERROR</strong>: Please enter a nickname.' ) );
	}

	/**
	 * Fires before the password and confirm password fields are checked for congruity.
	 *
	 * @since 1.5.1
	 *
	 * @param string $user_login The username.
	 * @param string $pass1     The password (passed by reference).
	 * @param string $pass2     The confirmed password (passed by reference).
	 */
	do_action_ref_array( 'check_passwords', array( $user->user_login, &$pass1, &$pass2 ) );

	// Check for blank password when adding a user.
	if ( ! $update && empty( $pass1 ) ) {
		$errors->add( 'pass', __( '<strong>ERROR</strong>: Please enter a password.' ), array( 'form-field' => 'pass1' ) );
	}

	// Check for "\" in password.
	if ( false !== strpos( wp_unslash( $pass1 ), '\\' ) ) {
		$errors->add( 'pass', __( '<strong>ERROR</strong>: Passwords may not contain the character "\\".' ), array( 'form-field' => 'pass1' ) );
	}

	// Checking the password has been typed twice the same.
	if ( ( $update || ! empty( $pass1 ) ) && $pass1 != $pass2 ) {
		$errors->add( 'pass', __( '<strong>ERROR</strong>: Please enter the same password in both password fields.' ), array( 'form-field' => 'pass1' ) );
	}

	if ( ! empty( $pass1 ) ) {
		$user->user_pass = $pass1;
	}

	if ( ! $update && isset( $_POST['user_login'] ) && ! validate_username( $_POST['user_login'] ) ) {
		$errors->add( 'user_login', __( '<strong>ERROR</strong>: This username is invalid because it uses illegal characters. Please enter a valid username.' ) );
	}

	if ( ! $update && username_exists( $user->user_login ) ) {
		$errors->add( 'user_login', __( '<strong>ERROR</strong>: This username is already registered. Please choose another one.' ) );
	}

	/** This filter is documented in wp-includes/user.php */
	$illegal_logins = (array) apply_filters( 'illegal_user_logins', array() );

	if ( in_array( strtolower( $user->user_login ), array_map( 'strtolower', $illegal_logins ) ) ) {
		$errors->add( 'invalid_username', __( '<strong>ERROR</strong>: Sorry, that username is not allowed.' ) );
	}

	/* checking email address */
	if ( empty( $user->user_email ) ) {
		$errors->add( 'empty_email', __( '<strong>ERROR</strong>: Please enter an email address.' ), array( 'form-field' => 'email' ) );
	} elseif ( ! is_email( $user->user_email ) ) {
		$errors->add( 'invalid_email', __( '<strong>ERROR</strong>: The email address isn&#8217;t correct.' ), array( 'form-field' => 'email' ) );
	} elseif ( ( $owner_id = email_exists( $user->user_email ) ) && ( ! $update || ( $owner_id != $user->ID ) ) ) {
		$errors->add( 'email_exists', __( '<strong>ERROR</strong>: This email is already registered, please choose another one.' ), array( 'form-field' => 'email' ) );
	}

	/**
	 * Fires before user profile update errors are returned.
	 *
	 * @since 2.8.0
	 *
	 * @param WP_Error $errors WP_Error object (passed by reference).
	 * @param bool     $update  Whether this is a user update.
	 * @param stdClass $user   User object (passed by reference).
	 */
	do_action_ref_array( 'user_profile_update_errors', array( &$errors, $update, &$user ) );

	if ( $errors->has_errors() ) {
		return $errors;
	}

	if ( $update ) {
		$user_id = wp_update_user( $user );
	} else {
		$user_id = wp_insert_user( $user );
		$notify  = isset( $_POST['send_user_notification'] ) ? 'both' : 'admin';

		/**
		 * Fires after a new user has been created.
		 *
		 * @since 4.4.0
		 *
		 * @param int    $user_id ID of the newly created user.
		 * @param string $notify  Type of notification that should happen. See wp_send_new_user_notifications()
		 *                        for more information on possible values.
		 */
		do_action( 'edit_user_created_user', $user_id, $notify );
	}
	return $user_id;
}