PHP同时连接多个mysql数据库

// 创建第一个数据库连接
$mysqli1 = new mysqli("localhost", "username1", "password1", "database1");

// 创建第二个数据库连接
$mysqli2 = new mysqli("localhost", "username2", "password2", "database2");

// 检查连接是否成功
if ($mysqli1->connect_errno || $mysqli2->connect_errno) {
    echo "数据库连接失败：" . $mysqli1->connect_error . $mysqli2->connect_error;
    exit();
}

// 执行数据库操作
// ...

// 关闭连接
$mysqli1->close();
$mysqli2->close();

// 创建第一个数据库连接
$dsn1 = "mysql:host=localhost;dbname=database1";
$username1 = "username1";
$password1 = "password1";
$pdo1 = new PDO($dsn1, $username1, $password1);

// 创建第二个数据库连接
$dsn2 = "mysql:host=localhost;dbname=database2";
$username2 = "username2";
$password2 = "password2";
$pdo2 = new PDO($dsn2, $username2, $password2);

// 执行数据库操作
// ...

// 关闭连接
$pdo1 = null;
$pdo2 = null;