diff --git a/.gitignore b/.gitignore
index fc43a6e..ea60caf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,5 @@
+.idea/
 vendor/
 .php_cs.cache
+.phpunit.result.cache
 composer.lock
diff --git a/.travis.yml b/.travis.yml
index ed5ee33..67c275d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,10 +5,9 @@ sudo: false
 matrix:
   fast_finish: true
   include:
-    - php: 7.1
-      env: CS_CHECK=1 STATIC_ANALYSIS=1
-    - php: 7.2
     - php: 7.3
+      env: CS_CHECK=1 STATIC_ANALYSIS=1
+    - php: 7.4
       env: CODE_COVERAGE=1
 
 cache:
diff --git a/composer.json b/composer.json
index cf173fb..dd92f3a 100644
--- a/composer.json
+++ b/composer.json
@@ -11,18 +11,18 @@
         }
     ],
     "require": {
-        "php": "^7.1"
+        "php": "^7.3"
     },
     "require-dev": {
-        "phpstan/phpstan": "^0.11",
-        "phpstan/phpstan-phpunit": "^0.11",
-        "phpunit/phpunit": "^7.5",
+        "phpstan/phpstan": "^0.12",
+        "phpstan/phpstan-phpunit": "^0.12",
+        "phpunit/phpunit": "^8.5",
         "roave/security-advisories": "dev-master",
-        "slam/php-cs-fixer-extensions": "^1.18",
+        "slam/php-cs-fixer-extensions": "^1.19",
         "slam/php-debug-r": "^1.6",
-        "slam/phpstan-extensions": "^3.6",
-        "symfony/console": "^4.3",
-        "thecodingmachine/phpstan-strict-rules": "^0.11"
+        "slam/phpstan-extensions": "^4.0",
+        "symfony/console": "^5.0",
+        "thecodingmachine/phpstan-strict-rules": "^0.12"
     },
     "autoload": {
         "psr-4": {
diff --git a/lib/ErrorHandler.php b/lib/ErrorHandler.php
index 9f1a745..754259f 100644
--- a/lib/ErrorHandler.php
+++ b/lib/ErrorHandler.php
@@ -5,24 +5,67 @@
 namespace Slam\ErrorHandler;
 
 use Doctrine\Common\Util\Debug as DoctrineDebug;
+use ErrorException;
+use Throwable;
 
 final class ErrorHandler
 {
+    /**
+     * @var bool
+     */
     private $autoExit = true;
+
+    /**
+     * @var null|bool
+     */
     private $cli;
+
+    /**
+     * @var null|int
+     */
     private $terminalWidth;
+
+    /**
+     * @var null|resource
+     */
     private $errorOutputStream;
+
+    /**
+     * @var bool
+     */
     private $hasColorSupport = false;
+
+    /**
+     * @var null|bool
+     */
     private $logErrors;
+
+    /**
+     * @var bool
+     */
     private $logVariables = true;
+
+    /**
+     * @var callable
+     */
     private $emailCallback;
+
+    /**
+     * @var array<int, bool>
+     */
     private $scream = [];
 
+    /**
+     * @var array<string, string>
+     */
     private static $colors = [
         '<error>'   => "\033[37;41m",
         '</error>'  => "\033[0m",
     ];
 
+    /**
+     * @var array<int, string>
+     */
     private static $errors = [
         \E_COMPILE_ERROR        => 'E_COMPILE_ERROR',
         \E_COMPILE_WARNING      => 'E_COMPILE_WARNING',
@@ -65,6 +108,7 @@ public function isCli(): bool
     {
         if (null === $this->cli) {
             $this->setCli(\PHP_SAPI === 'cli');
+            \assert(null !== $this->cli);
         }
 
         return $this->cli;
@@ -85,11 +129,15 @@ public function getTerminalWidth(): int
             }
 
             $this->setTerminalWidth((int) $width ?: 80);
+            \assert(null !== $this->terminalWidth);
         }
 
         return $this->terminalWidth;
     }
 
+    /**
+     * @param mixed $errorOutputStream
+     */
     public function setErrorOutputStream($errorOutputStream): void
     {
         if (! \is_resource($errorOutputStream)) {
@@ -100,10 +148,14 @@ public function setErrorOutputStream($errorOutputStream): void
         $this->hasColorSupport   = (\function_exists('posix_isatty') && @\posix_isatty($errorOutputStream));
     }
 
+    /**
+     * @return resource
+     */
     public function getErrorOutputStream()
     {
         if (null === $this->errorOutputStream) {
             $this->setErrorOutputStream(\STDERR);
+            \assert(null !== $this->errorOutputStream);
         }
 
         return $this->errorOutputStream;
@@ -118,6 +170,7 @@ public function logErrors(): bool
     {
         if (null === $this->logErrors) {
             $this->setLogErrors(! \interface_exists(\PHPUnit\Framework\Test::class));
+            \assert(null !== $this->logErrors);
         }
 
         return $this->logErrors;
@@ -133,11 +186,17 @@ public function logVariables(): bool
         return $this->logVariables;
     }
 
+    /**
+     * @param array<int, bool> $scream
+     */
     public function setScreamSilencedErrors(array $scream): void
     {
         $this->scream = $scream;
     }
 
+    /**
+     * @return array<int, bool>
+     */
     public function getScreamSilencedErrors(): array
     {
         return $this->scream;
@@ -149,6 +208,12 @@ public function register(): void
         \set_exception_handler([$this, 'exceptionHandler']);
     }
 
+    /**
+     * @param int    $errno
+     * @param string $errstr
+     * @param string $errfile
+     * @param int    $errline
+     */
     public function errorHandler($errno, $errstr = '', $errfile = '', $errline = 0): void
     {
         // Mandatory check for @ operator
@@ -156,10 +221,10 @@ public function errorHandler($errno, $errstr = '', $errfile = '', $errline = 0):
             return;
         }
 
-        throw new \ErrorException($errstr, $errno, $errno, $errfile, $errline);
+        throw new ErrorException($errstr, $errno, $errno, $errfile, $errline);
     }
 
-    public function exceptionHandler(\Throwable $exception): void
+    public function exceptionHandler(Throwable $exception): void
     {
         $this->logException($exception);
         $this->emailException($exception);
@@ -256,7 +321,7 @@ private function outputError(string $text): void
         \fwrite($this->getErrorOutputStream(), \str_replace(\array_keys(self::$colors), $this->hasColorSupport ? \array_values(self::$colors) : '', $text) . \PHP_EOL);
     }
 
-    public function logException(\Throwable $exception): void
+    public function logException(Throwable $exception): void
     {
         if (! $this->logErrors()) {
             return;
@@ -280,7 +345,7 @@ public function logException(\Throwable $exception): void
         } while ($exception = $exception->getPrevious());
     }
 
-    public function emailException(\Throwable $exception): void
+    public function emailException(Throwable $exception): void
     {
         if (! $this->logErrors()) {
             return;
@@ -348,16 +413,16 @@ public function emailException(\Throwable $exception): void
 
         try {
             $callback($subject, $bodyText);
-        } catch (\Throwable $e) {
+        } catch (Throwable $e) {
             $this->logException($e);
         }
     }
 
-    private function getExceptionCode(\Throwable $exception): string
+    private function getExceptionCode(Throwable $exception): string
     {
         $code = $exception->getCode();
-        if ($exception instanceof \ErrorException && isset(static::$errors[$code])) {
-            $code = static::$errors[$code];
+        if ($exception instanceof ErrorException && isset(self::$errors[$code])) {
+            $code = self::$errors[$code];
         }
 
         return (string) $code;
diff --git a/phpstan.neon b/phpstan.neon
index 38789a5..f14d2bc 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,5 +1,5 @@
 includes:
-    - vendor/phpstan/phpstan/conf/config.levelmax.neon
+    - phar://phpstan.phar/conf/config.levelmax.neon
     - vendor/phpstan/phpstan-phpunit/extension.neon
     - vendor/slam/phpstan-extensions/conf/slam-rules.neon
     - vendor/slam/phpstan-extensions/conf/thecodingmachine-rules.neon
@@ -15,3 +15,4 @@ parameters:
         - '#Variable \$_\w+ in isset\(\) always exists and is not nullable#'
         - '#Parameter \#1 \$error_handler of function set_error_handler expects#'
         - '#Offset .(no_exception_thrown.*|undefined_index). does not exist on array#'
+        - '#Expression .+arrayPerVerificaErrori.+ on a separate line does not do anything#'
diff --git a/tests/ErrorHandlerTest.php b/tests/ErrorHandlerTest.php
index e406fde..de7c07a 100644
--- a/tests/ErrorHandlerTest.php
+++ b/tests/ErrorHandlerTest.php
@@ -11,23 +11,41 @@
 
 final class ErrorHandlerTest extends TestCase
 {
+    /**
+     * @var string
+     */
     private $backupErrorLog;
+
+    /**
+     * @var string
+     */
     private $errorLog;
+
+    /**
+     * @var ErrorException
+     */
     private $exception;
-    private $emailsSent;
+
+    /**
+     * @var array<int, array<string, string>>
+     */
+    private $emailsSent = [];
+
+    /**
+     * @var ErrorHandler
+     */
     private $errorHandler;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         \ini_set('display_errors', (string) false);
-        $this->backupErrorLog = \ini_get('error_log');
+        $this->backupErrorLog = (string) \ini_get('error_log');
         $this->errorLog       = __DIR__ . \DIRECTORY_SEPARATOR . 'error_log_test';
         \touch($this->errorLog);
         \ini_set('error_log', $this->errorLog);
 
         $this->exception    = new ErrorException(\uniqid('normal_'), \E_USER_NOTICE);
-        $this->emailsSent   = [];
-        $this->errorHandler = new ErrorHandler(function (string $subject, string $body) {
+        $this->errorHandler = new ErrorHandler(function (string $subject, string $body): void {
             $this->emailsSent[] = [
                 'subject' => $subject,
                 'body'    => $body,
@@ -38,23 +56,23 @@ protected function setUp()
         $this->errorHandler->setTerminalWidth(50);
     }
 
-    protected function tearDown()
+    protected function tearDown(): void
     {
         \putenv('COLUMNS');
         \ini_set('error_log', $this->backupErrorLog);
         @\unlink($this->errorLog);
     }
 
-    public function testDefaultConfiguration()
+    public function testDefaultConfiguration(): void
     {
-        $errorHandler = new ErrorHandler(function () {
+        $errorHandler = new ErrorHandler(function (): void {
         });
 
-        static::assertTrue($errorHandler->isCli());
-        static::assertTrue($errorHandler->autoExit());
-        static::assertNotNull($errorHandler->getTerminalWidth());
-        static::assertSame(\STDERR, $errorHandler->getErrorOutputStream());
-        static::assertFalse($errorHandler->logErrors());
+        self::assertTrue($errorHandler->isCli());
+        self::assertTrue($errorHandler->autoExit());
+        self::assertNotNull($errorHandler->getTerminalWidth());
+        self::assertSame(\STDERR, $errorHandler->getErrorOutputStream());
+        self::assertFalse($errorHandler->logErrors());
 
         $errorHandler->setCli(false);
         $errorHandler->setAutoExit(false);
@@ -62,21 +80,21 @@ public function testDefaultConfiguration()
         $errorHandler->setErrorOutputStream($memoryStream = \fopen('php://memory', 'r+'));
         $errorHandler->setLogErrors(true);
 
-        static::assertFalse($errorHandler->isCli());
-        static::assertFalse($errorHandler->autoExit());
-        static::assertSame($width, $errorHandler->getTerminalWidth());
-        static::assertSame($memoryStream, $errorHandler->getErrorOutputStream());
-        static::assertTrue($errorHandler->logErrors());
+        self::assertFalse($errorHandler->isCli());
+        self::assertFalse($errorHandler->autoExit());
+        self::assertSame($width, $errorHandler->getTerminalWidth());
+        self::assertSame($memoryStream, $errorHandler->getErrorOutputStream());
+        self::assertTrue($errorHandler->logErrors());
 
         $errorHandler->setErrorOutputStream(\uniqid('not_a_stream_'));
-        static::assertSame($memoryStream, $errorHandler->getErrorOutputStream());
+        self::assertSame($memoryStream, $errorHandler->getErrorOutputStream());
     }
 
     /**
      * @runInSeparateProcess
      * @preserveGlobalState disabled
      */
-    public function testRegisterBuiltinHandlers()
+    public function testRegisterBuiltinHandlers(): void
     {
         $this->errorHandler->register();
         $arrayPerVerificaErrori = [];
@@ -91,15 +109,15 @@ public function testRegisterBuiltinHandlers()
      * @runInSeparateProcess
      * @preserveGlobalState disabled
      */
-    public function testScream()
+    public function testScream(): void
     {
         $scream = [
             \E_USER_WARNING => true,
         ];
 
-        static::assertEmpty($this->errorHandler->getScreamSilencedErrors());
+        self::assertEmpty($this->errorHandler->getScreamSilencedErrors());
         $this->errorHandler->setScreamSilencedErrors($scream);
-        static::assertSame($scream, $this->errorHandler->getScreamSilencedErrors());
+        self::assertSame($scream, $this->errorHandler->getScreamSilencedErrors());
 
         $this->errorHandler->register();
 
@@ -112,20 +130,20 @@ public function testScream()
         @ \trigger_error($warningMessage, \E_USER_WARNING);
     }
 
-    public function testHandleCliException()
+    public function testHandleCliException(): void
     {
         $memoryStream = \fopen('php://memory', 'r+');
-        static::assertIsResource($memoryStream);
+        self::assertIsResource($memoryStream);
         $this->errorHandler->setErrorOutputStream($memoryStream);
 
         $this->errorHandler->exceptionHandler($this->exception);
 
         \fseek($memoryStream, 0);
-        $output = \stream_get_contents($memoryStream);
-        static::assertContains($this->exception->getMessage(), $output);
+        $output = (string) \stream_get_contents($memoryStream);
+        self::assertStringContainsString($this->exception->getMessage(), $output);
     }
 
-    public function testHandleWebExceptionWithDisplay()
+    public function testHandleWebExceptionWithDisplay(): void
     {
         \ini_set('display_errors', (string) true);
         $this->errorHandler->setCli(false);
@@ -133,15 +151,15 @@ public function testHandleWebExceptionWithDisplay()
 
         \ob_start();
         $this->errorHandler->exceptionHandler($this->exception);
-        $output = \ob_get_clean();
+        $output = (string) \ob_get_clean();
 
-        static::assertContains($this->exception->getMessage(), $output);
+        self::assertStringContainsString($this->exception->getMessage(), $output);
 
-        $errorLogContent = \file_get_contents($this->errorLog);
-        static::assertContains($this->exception->getMessage(), $errorLogContent);
+        $errorLogContent = (string) \file_get_contents($this->errorLog);
+        self::assertStringContainsString($this->exception->getMessage(), $errorLogContent);
     }
 
-    public function testHandleWebExceptionWithoutDisplay()
+    public function testHandleWebExceptionWithoutDisplay(): void
     {
         \ini_set('display_errors', (string) false);
         $this->errorHandler->setCli(false);
@@ -149,21 +167,21 @@ public function testHandleWebExceptionWithoutDisplay()
 
         \ob_start();
         $this->errorHandler->exceptionHandler($this->exception);
-        $output = \ob_get_clean();
+        $output = (string) \ob_get_clean();
 
-        static::assertNotContains($this->exception->getMessage(), $output);
+        self::assertStringNotContainsString($this->exception->getMessage(), $output);
 
-        $errorLogContent = \file_get_contents($this->errorLog);
-        static::assertContains($this->exception->getMessage(), $errorLogContent);
+        $errorLogContent = (string) \file_get_contents($this->errorLog);
+        self::assertStringContainsString($this->exception->getMessage(), $errorLogContent);
     }
 
-    public function testLogErrorAndException()
+    public function testLogErrorAndException(): void
     {
         $this->errorHandler->setLogErrors(false);
 
         $this->errorHandler->logException($this->exception);
 
-        static::assertSame(0, \filesize($this->errorLog));
+        self::assertSame(0, \filesize($this->errorLog));
 
         $this->errorHandler->setLogErrors(true);
 
@@ -171,19 +189,19 @@ public function testLogErrorAndException()
 
         $this->errorHandler->logException($exception);
 
-        $errorLogContent = \file_get_contents($this->errorLog);
+        $errorLogContent = (string) \file_get_contents($this->errorLog);
 
-        static::assertContains($exception->getMessage(), $errorLogContent);
-        static::assertContains($this->exception->getMessage(), $errorLogContent);
+        self::assertStringContainsString($exception->getMessage(), $errorLogContent);
+        self::assertStringContainsString($this->exception->getMessage(), $errorLogContent);
     }
 
-    public function testEmailException()
+    public function testEmailException(): void
     {
         $this->errorHandler->setLogErrors(false);
 
         $this->errorHandler->emailException($this->exception);
 
-        static::assertEmpty($this->emailsSent);
+        self::assertEmpty($this->emailsSent);
 
         $this->errorHandler->setLogErrors(true);
 
@@ -193,21 +211,21 @@ public function testEmailException()
 
         $this->errorHandler->emailException($this->exception);
 
-        static::assertNotEmpty($this->emailsSent);
+        self::assertNotEmpty($this->emailsSent);
         $message = \current($this->emailsSent);
-        static::assertNotEmpty($message);
+        self::assertNotEmpty($message);
 
         $messageText = $message['body'];
-        static::assertContains($this->exception->getMessage(), $messageText);
-        static::assertContains($_SESSION[$key], $messageText);
-        static::assertContains($_POST[$key], $messageText);
+        self::assertStringContainsString($this->exception->getMessage(), $messageText);
+        self::assertStringContainsString($_SESSION[$key], $messageText);
+        self::assertStringContainsString($_POST[$key], $messageText);
     }
 
-    public function testCanHideVariablesFromEmail()
+    public function testCanHideVariablesFromEmail(): void
     {
-        static::assertTrue($this->errorHandler->logVariables());
+        self::assertTrue($this->errorHandler->logVariables());
         $this->errorHandler->setLogVariables(false);
-        static::assertFalse($this->errorHandler->logVariables());
+        self::assertFalse($this->errorHandler->logVariables());
 
         $this->errorHandler->setLogErrors(true);
 
@@ -217,20 +235,20 @@ public function testCanHideVariablesFromEmail()
 
         $this->errorHandler->emailException($this->exception);
 
-        static::assertNotEmpty($this->emailsSent);
+        self::assertNotEmpty($this->emailsSent);
         $message = \current($this->emailsSent);
-        static::assertNotEmpty($message);
+        self::assertNotEmpty($message);
 
         $messageText = $message['body'];
-        static::assertContains($this->exception->getMessage(), $messageText);
-        static::assertNotContains($_SESSION[$key], $messageText);
-        static::assertNotContains($_POST[$key], $messageText);
+        self::assertStringContainsString($this->exception->getMessage(), $messageText);
+        self::assertStringNotContainsString($_SESSION[$key], $messageText);
+        self::assertStringNotContainsString($_POST[$key], $messageText);
     }
 
-    public function testErroriNellInvioDellaMailVengonoComunqueLoggati()
+    public function testErroriNellInvioDellaMailVengonoComunqueLoggati(): void
     {
         $mailError    = \uniqid('mail_not_sent_');
-        $mailCallback = static function () use ($mailError) {
+        $mailCallback = static function () use ($mailError): void {
             throw new ErrorException($mailError, \E_USER_ERROR);
         };
         $errorHandler = new ErrorHandler($mailCallback);
@@ -238,12 +256,12 @@ public function testErroriNellInvioDellaMailVengonoComunqueLoggati()
 
         $errorHandler->emailException($this->exception);
 
-        $errorLogContent = \file_get_contents($this->errorLog);
-        static::assertNotContains($this->exception->getMessage(), $errorLogContent);
-        static::assertContains($mailError, $errorLogContent);
+        $errorLogContent = (string) \file_get_contents($this->errorLog);
+        self::assertStringNotContainsString($this->exception->getMessage(), $errorLogContent);
+        self::assertStringContainsString($mailError, $errorLogContent);
     }
 
-    public function testUsernameInEmailSubject()
+    public function testUsernameInEmailSubject(): void
     {
         $username = \uniqid('bob_');
         $_SESSION = ['custom_username_key' => $username];
@@ -253,25 +271,25 @@ public function testUsernameInEmailSubject()
 
         $message = \current($this->emailsSent);
 
-        static::assertContains($username, $message['subject']);
+        self::assertStringContainsString($username, $message['subject']);
     }
 
-    public function testTerminalWidthByEnv()
+    public function testTerminalWidthByEnv(): void
     {
         $width = \mt_rand(1000, 9000);
         \putenv(\sprintf('COLUMNS=%s', $width));
 
-        $errorHandler = new ErrorHandler(function () {
+        $errorHandler = new ErrorHandler(function (): void {
         });
 
-        static::assertSame($width, $errorHandler->getTerminalWidth());
+        self::assertSame($width, $errorHandler->getTerminalWidth());
 
         \putenv('COLUMNS');
 
-        $errorHandler = new ErrorHandler(function () {
+        $errorHandler = new ErrorHandler(function (): void {
         });
 
         $terminal = new Terminal();
-        static::assertSame($terminal->getWidth(), $errorHandler->getTerminalWidth());
+        self::assertSame($terminal->getWidth(), $errorHandler->getTerminalWidth());
     }
 }