add cs checking to ci flow

.github/workflows/code-style.yml

@@ -0,0 +1,25 @@
+name: Code style
+
+on: [push, pull_request]
+
+permissions:
+  contents: read
+
+jobs:
+  phpcs:
+    name: PHPCS
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '7.4'
+
+      - name: Install dependencies
+        run: composer update --prefer-dist --no-progress --no-suggest
+
+      - name: Run script
+        run: vendor/bin/phpcs

.gitignore

@@ -4,4 +4,7 @@
 .phan
 composer.lock
 
+/.phpcs-cache
+/phpcs.xml
+
 .phpunit.result.cache

composer.json

@@ -12,7 +12,8 @@
     "phan/phan": "^2.7"
   },
   "require-dev": {
-    "phpunit/phpunit": "^9"
+    "phpunit/phpunit": "^9",
+    "squizlabs/php_codesniffer": "^3.7"
   },
   "scripts": {
     "test": "vendor/bin/phpunit tests"

phpcs.xml.dist

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ruleset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/squizlabs/php_codesniffer/phpcs.xsd">
+
+    <arg name="extensions" value="php"/>
+    <rule ref="PSR12"/>
+
+    <file>.</file>
+</ruleset>