diff --git a/composer.json b/composer.json
index 53a327e..86dacf0 100644
--- a/composer.json
+++ b/composer.json
@@ -26,7 +26,7 @@
         "php": ">=7.4",
         "cache/adapter-common": "^1.0",
         "cache/hierarchical-cache": "^1.0",
-        "psr/cache": "^1.0 || ^2.0",
+        "psr/cache": "^1.0 || ^2.0 || ^3.0",
         "psr/simple-cache": "^1.0"
     },
     "require-dev": {
@@ -41,11 +41,13 @@
     "prefer-stable": true,
     "autoload": {
         "psr-4": {
-            "Cache\\Adapter\\PHPArray\\": ""
-        },
-        "exclude-from-classmap": [
-            "/Tests/"
-        ]
+            "Cache\\Adapter\\PHPArray\\": "src"
+        }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "Cache\\Adapter\\PHPArray\\Tests\\": "Tests"
+        }
     },
     "extra": {
         "branch-alias": {
diff --git a/ArrayCachePool.php b/src/ArrayCachePool.php
similarity index 92%
rename from ArrayCachePool.php
rename to src/ArrayCachePool.php
index e988145..c416e2f 100644
--- a/ArrayCachePool.php
+++ b/src/ArrayCachePool.php
@@ -75,7 +75,7 @@ protected function getItemWithoutGenerateCacheKey($key)
     /**
      * {@inheritdoc}
      */
-    protected function fetchObjectFromCache($key)
+    protected function fetchObjectFromCache(string $key): array
     {
         $keys = $this->getHierarchyKey($key);
 
@@ -96,7 +96,7 @@ protected function fetchObjectFromCache($key)
     /**
      * {@inheritdoc}
      */
-    protected function clearAllObjectsFromCache()
+    protected function clearAllObjectsFromCache(): bool
     {
         $this->cache = [];
 
@@ -106,7 +106,7 @@ protected function clearAllObjectsFromCache()
     /**
      * {@inheritdoc}
      */
-    protected function clearOneObjectFromCache($key)
+    protected function clearOneObjectFromCache(string $key): bool
     {
         $this->commit();
         $keys = $this->getHierarchyKey($key);
@@ -120,7 +120,7 @@ protected function clearOneObjectFromCache($key)
     /**
      * {@inheritdoc}
      */
-    protected function storeItemInCache(PhpCacheItem $item, $ttl)
+    protected function storeItemInCache(PhpCacheItem $item, null|int|\DateInterval $ttl): bool
     {
         $keys   = $this->getHierarchyKey($item->getKey());
         $value  = $item->get();
@@ -158,7 +158,7 @@ protected function getDirectValue($key)
     /**
      * {@inheritdoc}
      */
-    protected function getList($name)
+    protected function getList(string $name): iterable
     {
         if (!isset($this->cache[$name])) {
             $this->cache[$name] = [];
@@ -170,7 +170,7 @@ protected function getList($name)
     /**
      * {@inheritdoc}
      */
-    protected function removeList($name)
+    protected function removeList(string $name): bool
     {
         unset($this->cache[$name]);
 
@@ -180,7 +180,7 @@ protected function removeList($name)
     /**
      * {@inheritdoc}
      */
-    protected function appendListItem($name, $key)
+    protected function appendListItem(string $name, string $key)
     {
         $this->cache[$name][] = $key;
     }
@@ -188,7 +188,7 @@ protected function appendListItem($name, $key)
     /**
      * {@inheritdoc}
      */
-    protected function removeListItem($name, $key)
+    protected function removeListItem(string $name, string $key)
     {
         if (isset($this->cache[$name])) {
             foreach ($this->cache[$name] as $i => $item) {