执行 composer update 出现Warning: This development build of composer is over 60 days old.

composer update

Warning: This development build of composer is over 60 days old. It is recommended to update it by running "/usr/local/bin/composer self-update" to get the latest version.
PHP Warning:  require(/var/www/html/laravel/bootstrap/../vendor/autoload.php): failed to open stream: No such file or directory in /var/www/html/laravel/bootstrap/autoload.php on line 17
PHP Fatal error:  require(): Failed opening required '/var/www/html/laravel/bootstrap/../vendor/autoload.php' (include_path='.:/usr/share/php:/usr/share/pear') in /var/www/html/laravel/bootstrap/autoload.php on line 17
Script php artisan clear-compiled handling the pre-update-cmd event returned with an error

[RuntimeException]
Error Output: PHP Warning:  require(/var/www/html/laravel/bootstrap/../vendor/autoload.php): failed to open stream: No such file or directory in /var/www/html/laravel/bootstrap/autoload.
php on line 17
PHP Fatal error:  require(): Failed opening required '/var/www/html/laravel/bootstrap/../vendor/autoload.php' (include_path='.:/usr/share/php:/usr/share/pear') in /var/www/html/laravel/b
ootstrap/autoload.php on line 17

update [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--lock] [--no-plugins] [--no-custom-installers] [--no-autoloader] [--no-scripts] [--no-progress] [--with-dependencies] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [--ignore-platform-reqs] [--prefer-stable] [--prefer-lowest] [packages1] ... [packagesN]

/usr/local/bin/composer self-update

[Composer\Downloader\FilesystemException]
Filesystem exception:
Composer update failed: the "/usr/local/bin/composer" file could not be written

self-update [-r|--rollback] [--clean-backups] [--no-progress] [version]

chmod -R 777 /usr/local/bin/composer