mysql php释放内存

$mysqli = new mysqli("host", "user", "password", "database");
// 执行数据库操作
$mysqli->close(); // 关闭连接

try {
    $pdo = new PDO("mysql:host=host;dbname=database", "user", "password");
    // 执行数据库操作
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}
$pdo = null; // 关闭连接

$result = $mysqli->query("SELECT * FROM table");
while ($row = $result->fetch_assoc()) {
    // 处理每一行数据
}
$result->free(); // 释放结果集

try {
    $pdo = new PDO("mysql:host=host;dbname=database", "user", "password");
    $stmt = $pdo->query("SELECT * FROM table");
    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
        // 处理每一行数据
    }
} catch (PDOException $e) {
    echo "Query failed: " . $e->getMessage();
}
$pdo = null; // 关闭连接，同时也会释放结果集