get 从表中返回一行数据 get($table, $columns, $where) table [string] 表名. columns [string/array] 返回的字段列. where (optional) [array] WHERE 条件. Return: [string/array] 返回查询到的数据. 这个方法只能获取一条数据 $email = $database->get("account", "email", [ "user_id" => 1234 ]); // $email = "foo@bar.com" $profile = $database->get("account", [ "email", "gender", "location" ], [ "user_id" => 1234 ]); // $profile = array( // "email" => "foo@bar.com", // "gender" => "female", // "location" => "earth" // )