Many changes.

tests/ExampleClass.php

@@ -0,0 +1,59 @@
+<?php
+
+    class ExampleClass
+    {
+        /**
+         * @var array
+         */
+        private $data;
+
+        /**
+         * ExampleClass constructor.
+         */
+        public function __construct()
+        {
+            $this->data = [];
+        }
+
+        /**
+         * Sets a value in the data array
+         *
+         * @param string $key
+         * @param mixed $value
+         * @return void
+         */
+        public function set(string $key, mixed $value): void
+        {
+            $this->data[$key] = $value;
+        }
+
+        /**
+         * Gets a value from the data array
+         *
+         * @param string $key
+         * @return mixed
+         */
+        public function get(string $key): mixed
+        {
+            return $this->data[$key];
+        }
+
+        /**
+         * Checks if a key exists in the data array
+         *
+         * @param string $key
+         * @return bool
+         */
+        public function exists(string $key): bool
+        {
+            return isset($this->data[$key]);
+        }
+
+        /**
+         * @return void
+         */
+        public function clear(): void
+        {
+            $this->data = [];
+        }
+    }