diff --git a/.github/workflows/coding_standard.yaml b/.github/workflows/coding_standard.yaml
new file mode 100644
index 0000000..fa949ec
--- /dev/null
+++ b/.github/workflows/coding_standard.yaml
@@ -0,0 +1,20 @@
+name: Coding Standard
+
+on:
+    pull_request: null
+
+jobs:
+    coding_standard:
+        runs-on: ubuntu-latest
+
+        steps:
+            -   uses: actions/checkout@v2
+            # see https://github.com/shivammathur/setup-php
+            -   uses: shivammathur/setup-php@v2
+                with:
+                    php-version: 7.4
+                    coverage: none
+
+            -   run: composer install --no-progress --ansi
+
+            -   run: vendor/bin/ecs check-markdown README.md --ansi
\ No newline at end of file
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..49c63d2
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+composer.lock
+/vendor
\ No newline at end of file
diff --git a/.travis-build.php b/.travis-build.php
deleted file mode 100644
index 17a63fe..0000000
--- a/.travis-build.php
+++ /dev/null
@@ -1,77 +0,0 @@
-<?php
-
-$readMeFilepath = __DIR__ . '/README.md';
-$readMeFile = new SplFileObject($readMeFilepath);
-$readMeFile->setFlags(SplFileObject::DROP_NEW_LINE);
-
-$cliRedBackground = "\033[37;41m";
-$cliReset = "\033[0m";
-$exitStatus = 0;
-
-$indentationSteps = 3;
-$manIndex = 0;
-$linesWithSpaces = [];
-$tableOfContentsStarted = null;
-$currentTableOfContentsChapters = [];
-$chaptersFound = [];
-foreach ($readMeFile as $lineNumber => $line) {
-    if (preg_match('/\s$/', $line)) {
-        $linesWithSpaces[] = sprintf('%5s: %s', 1 + $lineNumber, $line);
-    }
-    if (preg_match('/^(?<depth>##+)\s(?<title>.+)/', $line, $matches)) {
-        if (null === $tableOfContentsStarted) {
-            $tableOfContentsStarted = true;
-            continue;
-        }
-        $tableOfContentsStarted = false;
-
-        if (strlen($matches['depth']) === 2) {
-            $depth = sprintf('  %s.', ++$manIndex);
-        } else {
-            $depth = sprintf(' %s*', str_repeat('  ', strlen($matches['depth']) - 1));
-        }
-
-        // ignore links in title
-        $matches['title'] = preg_replace('/\[([^\]]+)\]\((?:[^\)]+)\)/u', '$1', $matches['title']);
-
-        $link = $matches['title'];
-        $link = strtolower($link);
-        $link = str_replace(' ', '-', $link);
-        $link = preg_replace('/[^-\w]+/u', '', $link);
-
-        $chaptersFound[] = sprintf('%s [%s](#%s)', $depth, $matches['title'], $link);
-    }
-    if ($tableOfContentsStarted === true && isset($line[0])) {
-        $currentTableOfContentsChapters[] = $line;
-    }
-}
-
-if (count($linesWithSpaces)) {
-    fwrite(STDERR, sprintf("${cliRedBackground}The following lines end with a space character:${cliReset}\n%s\n\n",
-        implode(PHP_EOL, $linesWithSpaces)
-    ));
-    $exitStatus = 1;
-}
-
-$currentTableOfContentsChaptersFilename = __DIR__ . '/current-chapters';
-$chaptersFoundFilename = __DIR__ . '/chapters-found';
-
-file_put_contents($currentTableOfContentsChaptersFilename, implode(PHP_EOL, $currentTableOfContentsChapters));
-file_put_contents($chaptersFoundFilename, implode(PHP_EOL, $chaptersFound));
-
-$tableOfContentsDiff = shell_exec(sprintf('diff --unified %s %s',
-    escapeshellarg($currentTableOfContentsChaptersFilename),
-    escapeshellarg($chaptersFoundFilename)
-));
-
-@ unlink($currentTableOfContentsChaptersFilename);
-@ unlink($chaptersFoundFilename);
-
-if (!empty($tableOfContentsDiff)) {
-    fwrite(STDERR, sprintf("${cliRedBackground}The table of contents is not aligned:${cliReset}\n%s\n\n",
-        $tableOfContentsDiff
-    ));
-    $exitStatus = 1;
-}
-
-exit($exitStatus);
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index e4ea357..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,11 +0,0 @@
-language: php
-
-sudo: false
-
-php:
-  - nightly
-
-script: php .travis-build.php
-
-notifications:
-  email: false
diff --git a/README.md b/README.md
index 0e7551a..3fd40d9 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Clean Code PHP
+# Clean Code PHP
 
 ## Table of Contents
 
@@ -69,12 +69,16 @@ Although many developers still use PHP 5, most of the examples in this article o
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 $ymdstr = $moment->format('y-m-d');
 ```
 
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 $currentDate = $moment->format('y-m-d');
 ```
 
@@ -85,6 +89,8 @@ $currentDate = $moment->format('y-m-d');
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 getUserInfo();
 getUserData();
 getUserRecord();
@@ -94,6 +100,8 @@ getUserProfile();
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 getUser();
 ```
 
@@ -109,6 +117,8 @@ Make your names searchable.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 // What the heck is 448 for?
 $result = $serializer->serialize($data, 448);
 ```
@@ -116,6 +126,8 @@ $result = $serializer->serialize($data, 448);
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 $json = $serializer->serialize($data, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE);
 ```
 
@@ -124,6 +136,8 @@ $json = $serializer->serialize($data, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class User
 {
     // What the heck is 7 for?
@@ -142,11 +156,16 @@ $user->access ^= 2;
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 class User
 {
     public const ACCESS_READ = 1;
+
     public const ACCESS_CREATE = 2;
+
     public const ACCESS_UPDATE = 4;
+
     public const ACCESS_DELETE = 8;
 
     // User as default can read, create and update something
@@ -168,6 +187,8 @@ $user->access ^= User::ACCESS_CREATE;
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 $address = 'One Infinite Loop, Cupertino 95014';
 $cityZipCodeRegex = '/^[^,]+,\s*(.+?)\s*(\d{5})$/';
 preg_match($cityZipCodeRegex, $address, $matches);
@@ -180,6 +201,8 @@ saveCityZipCode($matches[1], $matches[2]);
 It's better, but we are still heavily dependent on regex.
 
 ```php
+declare(strict_types=1);
+
 $address = 'One Infinite Loop, Cupertino 95014';
 $cityZipCodeRegex = '/^[^,]+,\s*(.+?)\s*(\d{5})$/';
 preg_match($cityZipCodeRegex, $address, $matches);
@@ -193,6 +216,8 @@ saveCityZipCode($city, $zipCode);
 Decrease dependence on regex by naming subpatterns.
 
 ```php
+declare(strict_types=1);
+
 $address = 'One Infinite Loop, Cupertino 95014';
 $cityZipCodeRegex = '/^[^,]+,\s*(?<city>.+?)\s*(?<zipCode>\d{5})$/';
 preg_match($cityZipCodeRegex, $address, $matches);
@@ -210,6 +235,8 @@ than implicit.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 function isShopOpen($day): bool
 {
     if ($day) {
@@ -221,30 +248,27 @@ function isShopOpen($day): bool
                 return true;
             } elseif ($day === 'sunday') {
                 return true;
-            } else {
-                return false;
             }
-        } else {
             return false;
         }
-    } else {
         return false;
     }
+    return false;
 }
 ```
 
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 function isShopOpen(string $day): bool
 {
     if (empty($day)) {
         return false;
     }
 
-    $openingDays = [
-        'friday', 'saturday', 'sunday'
-    ];
+    $openingDays = ['friday', 'saturday', 'sunday'];
 
     return in_array(strtolower($day), $openingDays, true);
 }
@@ -257,27 +281,28 @@ function isShopOpen(string $day): bool
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 function fibonacci(int $n)
 {
     if ($n < 50) {
         if ($n !== 0) {
             if ($n !== 1) {
                 return fibonacci($n - 1) + fibonacci($n - 2);
-            } else {
-                return 1;
             }
-        } else {
-            return 0;
+            return 1;
         }
-    } else {
-        return 'Not supported';
+        return 0;
     }
+    return 'Not supported';
 }
 ```
 
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 function fibonacci(int $n): int
 {
     if ($n === 0 || $n === 1) {
@@ -285,7 +310,7 @@ function fibonacci(int $n): int
     }
 
     if ($n >= 50) {
-        throw new \Exception('Not supported');
+        throw new Exception('Not supported');
     }
 
     return fibonacci($n - 1) + fibonacci($n - 2);
@@ -319,6 +344,8 @@ for ($i = 0; $i < count($l); $i++) {
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 $locations = ['Austin', 'New York', 'San Francisco'];
 
 foreach ($locations as $location) {
@@ -341,10 +368,14 @@ variable name.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class Car
 {
     public $carMake;
+
     public $carModel;
+
     public $carColor;
 
     //...
@@ -354,10 +385,14 @@ class Car
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 class Car
 {
     public $make;
+
     public $model;
+
     public $color;
 
     //...
@@ -413,11 +448,13 @@ function createMicrobrewery(string $breweryName = 'Hipster Brew Co.'): void
 The simple comparison will convert the string in an integer.
 
 ```php
+declare(strict_types=1);
+
 $a = '42';
 $b = 42;
 
 if ($a != $b) {
-   // The expression will always pass
+    // The expression will always pass
 }
 ```
 
@@ -429,6 +466,8 @@ The string `42` is different than the integer `42`.
 The identical comparison will compare type and value.
 
 ```php
+declare(strict_types=1);
+
 $a = '42';
 $b = 42;
 
@@ -448,6 +487,8 @@ Null coalescing is a new operator [introduced in PHP 7](https://www.php.net/manu
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 if (isset($_GET['name'])) {
     $name = $_GET['name'];
 } elseif (isset($_POST['name'])) {
@@ -459,6 +500,8 @@ if (isset($_GET['name'])) {
 
 **Good:**
 ```php
+declare(strict_types=1);
+
 $name = $_GET['name'] ?? $_POST['name'] ?? 'nobody';
 ```
 
@@ -480,6 +523,8 @@ of the time a higher-level object will suffice as an argument.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class Questionnaire
 {
     public function __construct(
@@ -500,10 +545,14 @@ class Questionnaire
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 class Name
 {
     private $firstname;
+
     private $lastname;
+
     private $patronymic;
 
     public function __construct(string $firstname, string $lastname, string $patronymic)
@@ -519,7 +568,9 @@ class Name
 class City
 {
     private $region;
+
     private $district;
+
     private $city;
 
     public function __construct(string $region, string $district, string $city)
@@ -535,6 +586,7 @@ class City
 class Contact
 {
     private $phone;
+
     private $email;
 
     public function __construct(string $phone, string $email)
@@ -606,6 +658,8 @@ testing.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 function parseBetterPHPAlternative(string $code): void
 {
     $regexes = [
@@ -744,10 +798,12 @@ based on a boolean.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 function createFile(string $name, bool $temp = false): void
 {
     if ($temp) {
-        touch('./temp/'.$name);
+        touch('./temp/' . $name);
     } else {
         touch($name);
     }
@@ -757,6 +813,8 @@ function createFile(string $name, bool $temp = false): void
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 function createFile(string $name): void
 {
     touch($name);
@@ -764,7 +822,7 @@ function createFile(string $name): void
 
 function createTempFile(string $name): void
 {
-    touch('./temp/'.$name);
+    touch('./temp/' . $name);
 }
 ```
 
@@ -789,6 +847,8 @@ than the vast majority of other programmers.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 // Global variable referenced by following function.
 // If we had another function that used this name, now it'd be an array and it could break it.
 $name = 'Ryan McDermott';
@@ -802,12 +862,15 @@ function splitIntoFirstAndLastName(): void
 
 splitIntoFirstAndLastName();
 
-var_dump($name); // ['Ryan', 'McDermott'];
+var_dump($name);
+// ['Ryan', 'McDermott'];
 ```
 
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 function splitIntoFirstAndLastName(string $name): array
 {
     return explode(' ', $name);
@@ -816,8 +879,11 @@ function splitIntoFirstAndLastName(string $name): array
 $name = 'Ryan McDermott';
 $newName = splitIntoFirstAndLastName($name);
 
-var_dump($name); // 'Ryan McDermott';
-var_dump($newName); // ['Ryan', 'McDermott'];
+var_dump($name);
+// 'Ryan McDermott';
+
+var_dump($newName);
+// ['Ryan', 'McDermott'];
 ```
 
 **[⬆ back to top](#table-of-contents)**
@@ -833,9 +899,11 @@ that tried to do the same thing.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 function config(): array
 {
-    return  [
+    return [
         'foo' => 'bar',
     ];
 }
@@ -844,6 +912,8 @@ function config(): array
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 class Configuration
 {
     private $configuration = [];
@@ -855,7 +925,7 @@ class Configuration
 
     public function get(string $key): ?string
     {
-        // null coalescing operator 
+        // null coalescing operator
         return $this->configuration[$key] ?? null;
     }
 }
@@ -864,6 +934,8 @@ class Configuration
 Load configuration and create instance of `Configuration` class
 
 ```php
+declare(strict_types=1);
+
 $configuration = new Configuration([
     'foo' => 'bar',
 ]);
@@ -886,6 +958,8 @@ There is also very good thoughts by [Misko Hevery](http://misko.hevery.com/about
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class DBConnection
 {
     private static $instance;
@@ -895,7 +969,7 @@ class DBConnection
         // ...
     }
 
-    public static function getInstance(): DBConnection
+    public static function getInstance(): self
     {
         if (self::$instance === null) {
             self::$instance = new self();
@@ -913,6 +987,8 @@ $singleton = DBConnection::getInstance();
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 class DBConnection
 {
     public function __construct(string $dsn)
@@ -920,13 +996,15 @@ class DBConnection
         // ...
     }
 
-     // ...
+    // ...
 }
 ```
 
 Create instance of `DBConnection` class and configure it with [DSN](http://php.net/manual/en/pdo.construct.php#refsect1-pdo.construct-parameters).
 
 ```php
+declare(strict_types=1);
+
 $connection = new DBConnection($dsn);
 ```
 
@@ -939,6 +1017,8 @@ And now you must use instance of `DBConnection` in your application.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 if ($article->state === 'published') {
     // ...
 }
@@ -947,6 +1027,8 @@ if ($article->state === 'published') {
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 if ($article->isPublished()) {
     // ...
 }
@@ -959,13 +1041,14 @@ if ($article->isPublished()) {
 **Bad:**
 
 ```php
-function isDOMNodeNotPresent(\DOMNode $node): bool
+declare(strict_types=1);
+
+function isDOMNodeNotPresent(DOMNode $node): bool
 {
     // ...
 }
 
-if (!isDOMNodeNotPresent($node))
-{
+if (! isDOMNodeNotPresent($node)) {
     // ...
 }
 ```
@@ -973,7 +1056,9 @@ if (!isDOMNodeNotPresent($node))
 **Good:**
 
 ```php
-function isDOMNodePresent(\DOMNode $node): bool
+declare(strict_types=1);
+
+function isDOMNodePresent(DOMNode $node): bool
 {
     // ...
 }
@@ -999,6 +1084,8 @@ just do one thing.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class Airplane
 {
     // ...
@@ -1020,6 +1107,8 @@ class Airplane
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 interface Airplane
 {
     // ...
@@ -1070,6 +1159,8 @@ The first thing to consider is consistent APIs.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 function travelToTexas($vehicle): void
 {
     if ($vehicle instanceof Bicycle) {
@@ -1083,6 +1174,8 @@ function travelToTexas($vehicle): void
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 function travelToTexas(Vehicle $vehicle): void
 {
     $vehicle->travelTo(new Location('texas'));
@@ -1106,10 +1199,12 @@ Otherwise, do all of that but with PHP strict type declaration or strict mode.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 function combine($val1, $val2): int
 {
-    if (!is_numeric($val1) || !is_numeric($val2)) {
-        throw new \Exception('Must be of type Number');
+    if (! is_numeric($val1) || ! is_numeric($val2)) {
+        throw new Exception('Must be of type Number');
     }
 
     return $val1 + $val2;
@@ -1119,6 +1214,8 @@ function combine($val1, $val2): int
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 function combine(int $val1, int $val2): int
 {
     return $val1 + $val2;
@@ -1136,6 +1233,8 @@ in your version history if you still need it.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 function oldRequestModule(string $url): void
 {
     // ...
@@ -1153,6 +1252,8 @@ inventoryTracker('apples', $request, 'www.inventory-awesome.io');
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 function requestModule(string $url): void
 {
     // ...
@@ -1186,6 +1287,8 @@ Additionally, this is part of [Open/Closed](#openclosed-principle-ocp) principle
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class BankAccount
 {
     public $balance = 1000;
@@ -1253,6 +1356,8 @@ For more informations you can read the [blog post](http://fabien.potencier.org/p
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class Employee
 {
     public $name;
@@ -1264,12 +1369,15 @@ class Employee
 }
 
 $employee = new Employee('John Doe');
-echo 'Employee name: '.$employee->name; // Employee name: John Doe
+// Employee name: John Doe
+echo 'Employee name: ' . $employee->name;
 ```
 
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 class Employee
 {
     private $name;
@@ -1286,7 +1394,8 @@ class Employee
 }
 
 $employee = new Employee('John Doe');
-echo 'Employee name: '.$employee->getName(); // Employee name: John Doe
+// Employee name: John Doe
+echo 'Employee name: ' . $employee->getName();
 ```
 
 **[⬆ back to top](#table-of-contents)**
@@ -1315,9 +1424,12 @@ relationship (Human->Animal vs. User->UserDetails).
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class Employee
 {
     private $name;
+
     private $email;
 
     public function __construct(string $name, string $email)
@@ -1335,6 +1447,7 @@ class Employee
 class EmployeeTaxData extends Employee
 {
     private $ssn;
+
     private $salary;
 
     public function __construct(string $name, string $email, string $ssn, string $salary)
@@ -1352,9 +1465,12 @@ class EmployeeTaxData extends Employee
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 class EmployeeTaxData
 {
     private $ssn;
+
     private $salary;
 
     public function __construct(string $ssn, string $salary)
@@ -1369,7 +1485,9 @@ class EmployeeTaxData
 class Employee
 {
     private $name;
+
     private $email;
+
     private $taxData;
 
     public function __construct(string $name, string $email)
@@ -1378,7 +1496,7 @@ class Employee
         $this->email = $email;
     }
 
-    public function setTaxData(EmployeeTaxData $taxData)
+    public function setTaxData(EmployeeTaxData $taxData): void
     {
         $this->taxData = $taxData;
     }
@@ -1411,10 +1529,14 @@ on this topic written by [Marco Pivetta](https://github.com/Ocramius).
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class Car
 {
     private $make = 'Honda';
+
     private $model = 'Accord';
+
     private $color = 'white';
 
     public function setMake(string $make): self
@@ -1448,19 +1570,23 @@ class Car
 }
 
 $car = (new Car())
-  ->setColor('pink')
-  ->setMake('Ford')
-  ->setModel('F-150')
-  ->dump();
+    ->setColor('pink')
+    ->setMake('Ford')
+    ->setModel('F-150')
+    ->dump();
 ```
 
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 class Car
 {
     private $make = 'Honda';
+
     private $model = 'Accord';
+
     private $color = 'white';
 
     public function setMake(string $make): void
@@ -1510,6 +1636,8 @@ For more informations you can read [the blog post](https://ocramius.github.io/bl
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 final class Car
 {
     private $color;
@@ -1532,6 +1660,8 @@ final class Car
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 interface Vehicle
 {
     /**
@@ -1549,9 +1679,6 @@ final class Car implements Vehicle
         $this->color = $color;
     }
 
-    /**
-     * {@inheritdoc}
-     */
     public function getColor()
     {
         return $this->color;
@@ -1585,6 +1712,8 @@ your codebase.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class UserSettings
 {
     private $user;
@@ -1611,6 +1740,8 @@ class UserSettings
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 class UserAuth
 {
     private $user;
@@ -1629,6 +1760,7 @@ class UserAuth
 class UserSettings
 {
     private $user;
+
     private $auth;
 
     public function __construct(User $user)
@@ -1658,6 +1790,8 @@ add new functionalities without changing existing code.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 abstract class Adapter
 {
     protected $name;
@@ -1723,6 +1857,8 @@ class HttpRequester
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 interface Adapter
 {
     public function request(string $url): Promise;
@@ -1780,9 +1916,12 @@ get into trouble.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class Rectangle
 {
     protected $width = 0;
+
     protected $height = 0;
 
     public function setWidth(int $width): void
@@ -1820,7 +1959,7 @@ function printArea(Rectangle $rectangle): void
     $rectangle->setHeight(5);
 
     // BAD: Will return 25 for Square. Should be 20.
-    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->getArea()).PHP_EOL;
+    echo sprintf('%s has area %d.', get_class($rectangle), $rectangle->getArea()) . PHP_EOL;
 }
 
 $rectangles = [new Rectangle(), new Square()];
@@ -1903,6 +2042,8 @@ all of the settings. Making them optional helps prevent having a "fat interface"
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 interface Employee
 {
     public function work(): void;
@@ -1942,6 +2083,8 @@ class RobotEmployee implements Employee
 Not every worker is an employee, but every employee is a worker.
 
 ```php
+declare(strict_types=1);
+
 interface Workable
 {
     public function work(): void;
@@ -1999,6 +2142,8 @@ it makes your code hard to refactor.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 class Employee
 {
     public function work(): void
@@ -2034,6 +2179,8 @@ class Manager
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 interface Employee
 {
     public function work(): void;
@@ -2101,17 +2248,15 @@ updating multiple places any time you want to change one thing.
 **Bad:**
 
 ```php
+declare(strict_types=1);
+
 function showDeveloperList(array $developers): void
 {
     foreach ($developers as $developer) {
         $expectedSalary = $developer->calculateExpectedSalary();
         $experience = $developer->getExperience();
         $githubLink = $developer->getGithubLink();
-        $data = [
-            $expectedSalary,
-            $experience,
-            $githubLink
-        ];
+        $data = [$expectedSalary, $experience, $githubLink];
 
         render($data);
     }
@@ -2123,11 +2268,7 @@ function showManagerList(array $managers): void
         $expectedSalary = $manager->calculateExpectedSalary();
         $experience = $manager->getExperience();
         $githubLink = $manager->getGithubLink();
-        $data = [
-            $expectedSalary,
-            $experience,
-            $githubLink
-        ];
+        $data = [$expectedSalary, $experience, $githubLink];
 
         render($data);
     }
@@ -2137,17 +2278,15 @@ function showManagerList(array $managers): void
 **Good:**
 
 ```php
+declare(strict_types=1);
+
 function showList(array $employees): void
 {
     foreach ($employees as $employee) {
         $expectedSalary = $employee->calculateExpectedSalary();
         $experience = $employee->getExperience();
         $githubLink = $employee->getGithubLink();
-        $data = [
-            $expectedSalary,
-            $experience,
-            $githubLink
-        ];
+        $data = [$expectedSalary, $experience, $githubLink];
 
         render($data);
     }
@@ -2159,14 +2298,12 @@ function showList(array $employees): void
 It is better to use a compact version of the code.
 
 ```php
+declare(strict_types=1);
+
 function showList(array $employees): void
 {
     foreach ($employees as $employee) {
-        render([
-            $employee->calculateExpectedSalary(),
-            $employee->getExperience(),
-            $employee->getGithubLink()
-        ]);
+        render([$employee->calculateExpectedSalary(), $employee->getExperience(), $employee->getGithubLink()]);
     }
 }
 ```
diff --git a/composer.json b/composer.json
new file mode 100644
index 0000000..a9d7503
--- /dev/null
+++ b/composer.json
@@ -0,0 +1,10 @@
+{
+    "require": {
+        "php": "^7.2",
+        "symplify/easy-coding-standard": "^8.3"
+    },
+    "scripts": {
+        "check-cs": "vendor/bin/ecs check-markdown README.md",
+        "fix-cs": "vendor/bin/ecs check-markdown README.md --fix"
+    }
+}
diff --git a/ecs.php b/ecs.php
new file mode 100644
index 0000000..9555953
--- /dev/null
+++ b/ecs.php
@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+use PhpCsFixer\Fixer\PhpTag\BlankLineAfterOpeningTagFixer;
+use PhpCsFixer\Fixer\Strict\StrictComparisonFixer;
+use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
+use Symplify\EasyCodingStandard\ValueObject\Option;
+use Symplify\EasyCodingStandard\ValueObject\Set\SetList;
+
+return static function (ContainerConfigurator $containerConfigurator): void
+{
+    $parameters = $containerConfigurator->parameters();
+    $parameters->set(Option::PATHS, [__DIR__ . '/src', __DIR__ . '/config', __DIR__ . '/ecs.php']);
+
+    $parameters->set(Option::SETS, [
+        SetList::COMMON,
+        SetList::CLEAN_CODE,
+        SetList::DEAD_CODE,
+        SetList::PSR_12,
+        SetList::PHP_70,
+        SetList::PHP_71,
+        SetList::SYMPLIFY,
+    ]);
+
+    $parameters->set(Option::SKIP, [
+        BlankLineAfterOpeningTagFixer::class => null,
+        StrictComparisonFixer::class => null,
+    ]);
+};