diff --git a/src/Builder.php b/src/Builder.php
index 2c98dd2..0c3f403 100644
--- a/src/Builder.php
+++ b/src/Builder.php
@@ -73,7 +73,7 @@ public static function findOutputDir($vendor = null)
         if ($vendor) {
             $dir = $vendor . '/hiqdev/' . basename(dirname(__DIR__));
         } else {
-            $dir = dirname(__DIR__);
+            $dir = \dirname(__DIR__);
         }
 
         return $dir . static::OUTPUT_DIR_SUFFIX;
diff --git a/src/Helper.php b/src/Helper.php
index 62e937e..1a0b1df 100644
--- a/src/Helper.php
+++ b/src/Helper.php
@@ -27,20 +27,20 @@ class Helper
      */
     public static function mergeConfig(): array
     {
-        $args = func_get_args();
+        $args = \func_get_args();
         $res = array_shift($args) ?: [];
         foreach ($args as $items) {
-            if (!is_array($items)) {
+            if (!\is_array($items)) {
                 continue;
             }
             foreach ($items as $k => $v) {
-                if (is_int($k)) {
+                if (\is_int($k)) {
                     if (isset($res[$k])) {
                         $res[] = $v;
                     } else {
                         $res[$k] = $v;
                     }
-                } elseif (is_array($v) && isset($res[$k]) && is_array($res[$k])) {
+                } elseif (\is_array($v) && isset($res[$k]) && \is_array($res[$k])) {
                     $res[$k] = self::mergeConfig($res[$k], $v);
                 } else {
                     $res[$k] = $v;
@@ -67,6 +67,7 @@ public static function exportDefines(array $defines): string
      * In contrast to var_dump outputs Closures as PHP code.
      * @param mixed $value
      * @return string
+     * @throws \ReflectionException
      */
     public static function exportVar($value): string
     {
@@ -93,9 +94,9 @@ private static function collectClosures(&$input): array
     {
         static $closureNo = 1;
         $closures = [];
-        if (is_array($input)) {
+        if (\is_array($input)) {
             foreach ($input as &$value) {
-                if (is_array($value) || $value instanceof Closure) {
+                if (\is_array($value) || $value instanceof Closure) {
                     $closures = array_merge($closures, self::collectClosures($value));
                 }
             }
@@ -114,6 +115,7 @@ private static function collectClosures(&$input): array
      * Based on http://www.metashock.de/2013/05/dump-source-code-of-closure-in-php/.
      * @param Closure $closure
      * @return string
+     * @throws \ReflectionException
      */
     public static function dumpClosure(Closure $closure): string
     {
diff --git a/src/Package.php b/src/Package.php
index 601f1b1..6b8e006 100644
--- a/src/Package.php
+++ b/src/Package.php
@@ -44,6 +44,8 @@ class Package
      */
     protected $filesystem;
 
+    private $composer;
+
     public function __construct(PackageInterface $package, Composer $composer)
     {
         $this->package = $package;
@@ -73,6 +75,7 @@ public function collectAliases(): array
     /**
      * Prepare aliases.
      * @param string 'psr-0' or 'psr-4'
+     * @param bool $dev
      * @return array
      */
     protected function prepareAliases($psr, $dev = false)
@@ -244,8 +247,7 @@ protected function readRawData(): array
 
     /**
      * Builds path inside of a package.
-     * @param Package $package
-     * @param mixed $path can be absolute or relative
+     * @param string $file
      * @return string absolute paths will stay untouched
      */
     public function preparePath(string $file): string
diff --git a/src/Plugin.php b/src/Plugin.php
index 7aef851..be70727 100644
--- a/src/Plugin.php
+++ b/src/Plugin.php
@@ -24,7 +24,7 @@
  */
 class Plugin implements PluginInterface, EventSubscriberInterface
 {
-    const EXTRA_OPTION_NAME = 'config-plugin';
+    private const EXTRA_OPTION_NAME = 'config-plugin';
 
     /**
      * @var Package[] the array of active composer packages
@@ -41,6 +41,8 @@ class Plugin implements PluginInterface, EventSubscriberInterface
         'params'  => [],
     ];
 
+    protected $colors = ['red', 'green', 'yellow', 'cyan', 'magenta', 'blue'];
+
     /**
      * @var array package name => configs as listed in `composer.json`
      */
@@ -304,6 +306,4 @@ protected function showDepsTree()
             $this->io->write(sprintf('%s - <fg=%s;options=bold>%s</> %s %s', $indent, $color, $name, $package->getFullPrettyVersion(), $showdeps));
         }
     }
-
-    protected $colors = ['red', 'green', 'yellow', 'cyan', 'magenta', 'blue'];
 }
diff --git a/src/configs/Config.php b/src/configs/Config.php
index 0aa009a..73a5f4d 100644
--- a/src/configs/Config.php
+++ b/src/configs/Config.php
@@ -95,8 +95,7 @@ protected function loadFile($path): array
 
     /**
      * Merges given configs and writes at given name.
-     * @param mixed $name
-     * @param array $configs
+     * @return Config
      */
     public function build(): self
     {
@@ -130,6 +129,8 @@ protected function writeFile(string $path, array $data): void
      * @param string|array $data
      * @param bool $withEnv
      * @param bool $withDefines
+     * @throws FailedWriteException
+     * @throws \ReflectionException
      */
     protected function writePhpFile(string $path, $data, bool $withEnv, bool $withDefines): void
     {
@@ -146,6 +147,7 @@ protected function writePhpFile(string $path, $data, bool $withEnv, bool $withDe
     /**
      * @param array $vars array to be exported
      * @return string
+     * @throws \ReflectionException
      */
     protected function renderVars(array $vars): string
     {
@@ -163,6 +165,7 @@ protected function replaceMarkers(string $content): string
      * Writes file if content changed.
      * @param string $path
      * @param string $content
+     * @throws FailedWriteException
      */
     protected static function putFile($path, $content): void
     {
diff --git a/src/configs/ConfigFactory.php b/src/configs/ConfigFactory.php
index e663f1d..1d2f889 100644
--- a/src/configs/ConfigFactory.php
+++ b/src/configs/ConfigFactory.php
@@ -20,8 +20,6 @@
  */
 class ConfigFactory
 {
-    private static $loaders;
-
     private static $knownTypes = [
         '__rebuild'     => Rebuild::class,
         '__files'       => System::class,
@@ -33,13 +31,13 @@ class ConfigFactory
     ];
 
     /**
+     * @param Builder $builder
+     * @param string $name
      * @return Config
      */
-    public static function create(Builder $builder, string $name)
+    public static function create(Builder $builder, string $name): Config
     {
-        $class = isset(static::$knownTypes[$name])
-            ? static::$knownTypes[$name]
-            : Config::class;
+        $class = static::$knownTypes[$name] ?? Config::class;
 
         return new $class($builder, $name);
     }
diff --git a/src/readers/EnvReader.php b/src/readers/EnvReader.php
index 7587947..645c459 100644
--- a/src/readers/EnvReader.php
+++ b/src/readers/EnvReader.php
@@ -10,6 +10,8 @@
 
 namespace hiqdev\composer\config\readers;
 
+use hiqdev\composer\config\exceptions\UnsupportedFileTypeException;
+
 /**
  * EnvReader - reads `.env` files.
  *
diff --git a/src/readers/YamlReader.php b/src/readers/YamlReader.php
index c7b6caa..746cf32 100644
--- a/src/readers/YamlReader.php
+++ b/src/readers/YamlReader.php
@@ -10,6 +10,8 @@
 
 namespace hiqdev\composer\config\readers;
 
+use hiqdev\composer\config\exceptions\UnsupportedFileTypeException;
+
 /**
  * YamlReader - reads YAML files.
  *