如何将mySQL中具有相同值的行分组到php中？

$servername = "数据库服务器地址";
$username = "用户名";
$password = "密码";
$dbname = "数据库名";

// 使用mysqli扩展连接到MySQL数据库
$conn = new mysqli($servername, $username, $password, $dbname);

// 使用PDO扩展连接到MySQL数据库
$conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);

$sql = "SELECT age, COUNT(*) as count FROM users GROUP BY age";

// 使用mysqli扩展执行查询
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        echo "Age: " . $row["age"] . " Count: " . $row["count"] . "<br>";
    }
} else {
    echo "No results found";
}

// 使用PDO扩展执行查询
$stmt = $conn->prepare($sql);
$stmt->execute();

if ($stmt->rowCount() > 0) {
    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
        echo "Age: " . $row["age"] . " Count: " . $row["count"] . "<br>";
    }
} else {
    echo "No results found";
}