［PHP］DB2のdb2_fetch_objectでオブジェクト指向なデータ取得！

こんにちは！今回は、DB2データベースのdb2_fetch_object関数について、実践的に解説していきます。この関数を使うと、クエリ結果を標準オブジェクトとして取得できます。

db2_fetch_objectとは？🎯
基本的な使い方
基本的な使用例
1. 例1：シンプルなデータ取得
実践的な使用例
エラーハンドリング
実装のTips 💡
まとめ

db2_fetch_objectとは？🎯

DB2のクエリ結果を1行ずつ取得し、その行データをオブジェクトとして返す関数です。カラム名がオブジェクトのプロパティとして使用できます。

基本的な使い方

$obj = db2_fetch_object($statement);

基本的な使用例

例1：シンプルなデータ取得

$sql = "SELECT emp_id, name, department FROM employees";
$stmt = db2_exec($connection, $sql);

while ($emp = db2_fetch_object($stmt)) {
    echo "社員ID: " . $emp->EMP_ID . "\n";
    echo "名前: " . $emp->NAME . "\n";
    echo "部署: " . $emp->DEPARTMENT . "\n";
    echo "---------------\n";
}

実践的な使用例

例1：従業員クラスと組み合わせる

class Employee {
    private $id;
    private $name;
    private $department;
    private $salary;

    public function __construct($data = null) {
        if ($data) {
            $this->id = $data->EMP_ID;
            $this->name = $data->NAME;
            $this->department = $data->DEPARTMENT;
            $this->salary = $data->SALARY;
        }
    }

    public function getFormattedSalary() {
        return number_format($this->salary) . '円';
    }

    public function getDisplayName() {
        return "{$this->name}（{$this->department}）";
    }
}

function getEmployees($connection) {
    $sql = "SELECT * FROM employees";
    $stmt = db2_exec($connection, $sql);
    $employees = [];

    while ($obj = db2_fetch_object($stmt)) {
        $employees[] = new Employee($obj);
    }

    return $employees;
}

例2：部署管理システム

class Department {
    private $employees = [];
    private $name;
    private $totalSalary = 0;

    public function __construct($name) {
        $this->name = $name;
    }

    public function addEmployee($emp) {
        $this->employees[] = $emp;
        $this->totalSalary += $emp->SALARY;
    }

    public function getStats() {
        return [
            'name' => $this->name,
            'count' => count($this->employees),
            'totalSalary' => $this->totalSalary,
            'avgSalary' => $this->totalSalary / count($this->employees)
        ];
    }
}

function getDepartmentStats($connection) {
    $sql = "SELECT * FROM employees ORDER BY department";
    $stmt = db2_exec($connection, $sql);
    $departments = [];

    while ($emp = db2_fetch_object($stmt)) {
        if (!isset($departments[$emp->DEPARTMENT])) {
            $departments[$emp->DEPARTMENT] = new Department($emp->DEPARTMENT);
        }
        $departments[$emp->DEPARTMENT]->addEmployee($emp);
    }

    return $departments;
}

例3：JSONレスポンス生成

function getEmployeesJSON($connection) {
    $sql = "SELECT * FROM employees";
    $stmt = db2_exec($connection, $sql);
    $employees = [];

    while ($emp = db2_fetch_object($stmt)) {
        $employeeData = [
            'id' => $emp->EMP_ID,
            'name' => $emp->NAME,
            'department' => $emp->DEPARTMENT,
            'salary' => (float)$emp->SALARY,
            'fullInfo' => sprintf(
                '%s（%s部署）',
                $emp->NAME,
                $emp->DEPARTMENT
            )
        ];
        $employees[] = $employeeData;
    }

    return json_encode($employees);
}

エラーハンドリング

function fetchEmployeeData($connection, $empId) {
    try {
        $sql = "SELECT * FROM employees WHERE emp_id = ?";
        $stmt = db2_prepare($connection, $sql);

        if (!$stmt) {
            throw new Exception("準備されたステートメントの作成に失敗");
        }

        db2_bind_param($stmt, 1, $empId, DB2_PARAM_IN);

        if (!db2_execute($stmt)) {
            throw new Exception("クエリの実行に失敗");
        }

        $emp = db2_fetch_object($stmt);

        if (!$emp) {
            throw new Exception("従業員が見つかりません");
        }

        return $emp;

    } catch (Exception $e) {
        error_log("Error: " . $e->getMessage());
        return null;
    }
}

実装のTips 💡

1. カスタムクラスでの活用

class EmployeeRecord {
    public function __get($name) {
        // プロパティが存在しない場合の処理
        return null;
    }

    public function getFullName() {
        return $this->LAST_NAME . ' ' . $this->FIRST_NAME;
    }
}

function getCustomEmployees($connection) {
    $stmt = db2_exec($connection, "SELECT * FROM employees");
    $employees = [];

    while ($emp = db2_fetch_object($stmt, 'EmployeeRecord')) {
        $employees[] = $emp;
    }

    return $employees;
}

2. メモリ効率の良い処理

function processLargeDataset($connection) {
    $stmt = db2_exec($connection, "SELECT * FROM large_table");

    while ($obj = db2_fetch_object($stmt)) {
        processObject($obj);
        unset($obj);  // メモリ解放
    }
}

3. データ検証

function validateEmployee($emp) {
    return (
        isset($emp->EMP_ID) &&
        !empty($emp->NAME) &&
        is_numeric($emp->SALARY) &&
        $emp->SALARY > 0
    );
}