回答です

answer/Ex01.php

@@ -0,0 +1,16 @@
+<?php
+// Ex01_answer.php
+
+$dsn = "mysql:host=localhost;dbname=employee_db;charset=utf8";
+$username = "rezouser";
+$password = "Rezo_0000";
+
+try {
+    $pdo = new PDO($dsn, $username, $password);
+    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
+    echo "接続しました";
+} catch (PDOException $e) {
+    echo "接続エラー: " . $e->getMessage();
+} finally {
+    $pdo = null;
+}