Any command with Artisan is not working

Question

I went to try to install a dependency: https://github.com/barryvdh/laravel-dompdf . But at the end of the installation, an error message appeared:

Installation failed, reverting ./composer.json to its original content.

now no command php artisan algo works, this error presents:

[Symfony\Component\Debug\Exception\FatalErrorException] syntax error, unexpected ')'

I also tried to remove the folder vendor and install again. Here is another error shown:

Generating autoload files
> Illuminate\Foundation\ComposerScripts::postInstall
> php artisan optimize


  [Symfony\Component\Debug\Exception\FatalErrorException]
  syntax error, unexpected ')'


Script php artisan optimize handling the post-install-cmd event returned with error code 255

Man composer.json

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "type": "project",
    "require": {
        "php": ">=5.5.9",
        "laravel/framework": "5.2.*"
    },
    "require-dev": {
        "fzaninotto/faker": "~1.4",
        "mockery/mockery": "0.9.*",
        "phpunit/phpunit": "~4.0",
        "symfony/css-selector": "2.8.*|3.0.*",
        "symfony/dom-crawler": "2.8.*|3.0.*"
    },
    "autoload": {
        "classmap": [
            "database",
            "app/Libraries/Classes",
            "app/Libraries/Classes/HTML",
            "app/Libraries/Classes/Script"
        ],
        "psr-4": {
            "App\\": "app/"
        }
    },
    "autoload-dev": {
        "classmap": [
            "tests/TestCase.php"
        ]
    },
    "scripts": {
        "post-root-package-install": [
            "php -r \"copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ],
        "post-install-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postInstall",
            "php artisan optimize"
        ],
        "post-update-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postUpdate",
            "php artisan optimize"
        ]
    },
    "config": {
        "preferred-install": "dist"
    }
}