Add linting stage

.php_cs.php

@@ -0,0 +1,14 @@
+<?php
+
+$finder = PhpCsFixer\Finder::create()
+    ->in('.')
+;
+
+return PhpCsFixer\Config::create()
+    ->setRules([
+        '@PSR2' => true,
+        'array_syntax' => ['syntax' => 'short'],
+    ])
+    ->setFinder($finder)
+    ->setUsingCache(false)
+;

.phpstan.neon

@@ -0,0 +1,4 @@
+parameters:
+    ignoreErrors:
+        - '#Result of method React\\Socket\\ServerInterface::close\(\) \(void\) is used#'
+        - '#Call to an undefined static method Symfony\\Component\\Process\\ProcessUtils::escapeArgument\(\)#'

.travis.yml

@@ -0,0 +1,29 @@
+sudo: false
+
+language: php
+
+install:
+  - composer validate
+  - composer install
+
+matrix:
+  fast_finish: true
+
+jobs:
+  include:
+    - stage: lint
+      php: 7.1
+      install:
+        - rm -f ~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/xdebug.ini
+        - composer require "phpstan/phpstan" "friendsofphp/php-cs-fixer:^2.8"
+      script:
+        # Static analyzer check
+        - ./vendor/bin/phpstan analyze -c .phpstan.neon --level=4 --no-progress Bootstraps Bridges Laravel
+        # Check the code style
+        - IFS=$'\n'; COMMIT_SCA_FILES=($(git diff --name-only --diff-filter=ACMRTUXB "${TRAVIS_COMMIT_RANGE}")); unset IFS
+        - ./vendor/bin/php-cs-fixer fix --config=.php_cs.php -v --dry-run --stop-on-violation --using-cache=no --path-mode=intersection -- "${COMMIT_SCA_FILES[@]}"
+
+# Cache package sources
+cache:
+  directories:
+    - $HOME/.composer/cache