<?php
    class DatabaseConnection
    {
        private $strEngine;
        private $strHost;
        private $strDatabaseName;
        private $strUsername;
        private $strPassword;
        private $pdo;

        public function __construct(
            $strEngine          = null,
            $strHost            = null,
            $strDatabaseName    = null,
            $strUsername        = null,
            $strPassword        = null)
        {
            $this->strEngine = $strEngine;

            switch ($strEngine)
            {
                case "sqlsrv":
                    $this->pdo = new PDO(
                        "sqlsrv:Server={$strHost};Database={$strDatabaseName}",
                        $strUsername,
                        $strPassword);
                    break;

                case "mysql":
                    $this->pdo = new PDO(
                        "mysql:host={$strHost};dbname={$strDatabaseName}",
                        $strUsername,
                        $strPassword);
                    break;

                case "sqlite":
                    $strFileName = $strHost;
                    if ($strFileName == null || strlen($strFileName) < 1)
                        $strFileName = ":memory:";

                    $this->pdo = new PDO("sqlite:{$strFileName}");
                    break;

                default:
                    throw new Exception("Unknown database engine {$strEngine}.");
            }

            $this->pdo->setAttribute(
                PDO::ATTR_ERRMODE,
                PDO::ERRMODE_EXCEPTION);
        }

        public function query($input)
        {
            $varArgs = self::flatten(func_get_args());

            if (count($varArgs) < 1)
                throw new Exception("query takes at least one argument, the query!");

            $strQuery = array_shift($varArgs);
            $strQuery = file_exists("db/{$strQuery}")?
                file_get_contents("db/{$strQuery}") :
                $strQuery;

            if ($this->strEngine == "sqlsrv")
                $strQuery = "set nocount on; {$strQuery}";

            $varStatement = $this->pdo->prepare($strQuery);

            if (count($varArgs) > 0)
                    $varStatement->execute($varArgs);
            else    $varStatement->execute();

            $varTemp    = array();
            $varOutput  = array();

            // Engines that do not support multiple rowsets:
            if (in_array($this->strEngine, array("sqlite")))
            {
                while ($varRow = $varStatement->fetch())
                {
                    $varNewRow = array();

                    foreach ($varRow as $k => $v)
                        if (!is_numeric($k))
                            $varNewRow[$k] = $v;

                    $varOutput[] = $varNewRow;
                }

                return $varOutput;
            }

            do
            {
                try { $varTemp[] = $varStatement->fetchAll(); }
                catch (Exception $x) {}
            }
            while ($varStatement->nextRowset());

            foreach ($varTemp as $i => $varSet)
                foreach ($varSet as $j => $varRow)
                {
                    $varNewRow = array();

                    foreach ($varRow as $k => $v)
                        if (!is_numeric($k))
                            $varNewRow[$k] = $v;

                    $varOutput[] = $varNewRow;
                }

            return $varOutput;
        }

        //
        //
        //
        //
        //
        //
        //

        // Used to combine a mixture of values and arrays of values as one flat array of values in the order they arrive in. For example: self::flatten("a", ["b", "c", ["d", "e", "f"], "g"], "h") should return an array of ["a", "b", "c", "d", "e", "f", "g", "h"].
        private static function flatten(...$args)
        {
            if (is_null($args))
                return array();

            if (count($args) > 0)
            {
                $varOutput = array();
                $varFirst = array_shift($args);

                if (is_array($varFirst))
                    foreach ($varFirst as $varItem)
                        $varOutput = array_merge($varOutput, self::flatten($varItem));
                else
                array_push($varOutput, $varFirst);

                if (count($args) > 0)
                    $varOutput = array_merge($varOutput, self::flatten($args));

                return $varOutput;
            }
            else
            return array();
        }
    }
?>