您的论点顺序错误。根据文档，连接优先
<?phprequire("constants.php");// 1. Create a database connection$connection = mysqli_connect(DB_SERVER,DB_USER,DB_PASS);if (!$connection) { error_log("Failed to connect to MySQL: " . mysqli_error($connection)); die('Internal server error');}// 2. Select a database to use $db_select = mysqli_select_db($connection, DB_NAME);if (!$db_select) { error_log("Database selection failed: " . mysqli_error($connection)); die('Internal server error');}?>
