What’s Wrong With The Existing MSSQL Extension For PHP?

… or, why do we need an improved SQL Server extension for PHP? :)

The existing MSSQL extension works well, but has a few practical limitations that have to be worked around.

• Limited to varchar(255) support
• No support for unicode columns like nvarchar
• No PDO drivers
• Poor error reporting

Now some of these issues are fixed, however Microsoft native Sql driver is still not used. As I’ve mentioned before, there are to ways to use native driver in PHP now:

1. As PHP extension
2. Through ODBC

However, none of these is available in Zend Framwork. So my task now (because of Winphp competition) is to come up with something what can be used to connect to Microsft Sql database with the new driver. To start with, lets look how standard DB config looks like:

;application/config/application.ini, ZF 1.8
resources.db.adapter = PDO_MYSQL
resources.db.params.host = localhost
resources.db.params.username = usr
resources.db.params.password = psw
resources.db.params.dbname = zf-tutorial

My goal is to change it as minimal as possible to allow easy db’s migration. To test ODBC connector I downloaded this class and renamed it to Add_Db_Adapter_Pdo_Odbc (because it’s not a good idea to change something in actual Zend Framework library). To use it in your code you need to change config file to something like this:

resources.db.adapter = PDO_ODBC
resources.db.params.adapterNamespace = App_Db_Adapter
resources.db.params.username = usr
resources.db.params.password = psw
resources.db.params.dbname = "Driver={SQL Native Client};
Server=localhost\SQLEXPRESS;Database=zf-tutorial;"

Note dbname string – now it has not only database name, but also driver information and host. I guess such format is chosen because dns’ for ODBC are very different for different providers, so to make things easier you just supply whole string, not it’s parts (driver, server/file, etc.). Don’t forget to use correct server host – for some strange reasons 127.0.0.1 refused to work for me.

Problem with ODBC is that it’s too general: ODBC supports a lot databases, hence they each can have something different (correct me if I’m wrong). That’s why I’m thinking about refactoring this class to App_Db_Adapter_Pdo_Odbc_Abstract abstract class and separate classes for different drivers. Although this class works fine for MSSQL, so can be used as is.

To test PHP extension there are no classes at all (at least I haven’t found, only in Adodb). So I decided to implement one myself – with a help of SqlSrv API Reference and Zend_Db_Adapter_Abstract abstract class I quite quickly came up with a working solution App_Db_Adapter_Mssql. Connection configuration looks the same:

resources.db.adapter = MSSQL
resources.db.params.adapterNamespace = App_Db_Adapter
resources.db.params.host = localhost\SQLEXPRESS
resources.db.params.username = usr
resources.db.params.password = psw
resources.db.params.dbname = zf-tutorial

I’ve tested both classes with the same application from previous post and benchmark results surprised me. They were equal! With a small variations page generation times were about 140 ms (all default settings, IIS7, MSSQL Express). Why? SQL server driver for PHP is open source, so if you look at it’s source you would find (C++):

SQLRETURN build_connection_string_and_set_conn_attr(
       sqlsrv_conn const* conn, const char* server, zval const* options,
       __inout std::string& connection_string TSRMLS_DC )
{
   ...
 
   connection_string = "Driver={SQL Native Client};Server=";
   connection_string += server;
   connection_string += ";";
 
   ...
 
   for( zend_hash_internal_pointer_reset( oht );
         zend_hash_has_more_elements( oht ) == SUCCESS;
         zend_hash_move_forward( oht )) {
 
      ...
 
       if( NO_ATTRIBUTE == ret.attr ) {
           if( ret.add ) {
               connection_string += key;
               connection_string += "={";
               connection_string += ret.str_value;
               connection_string += "};";
           }
       }
       ...
   }
 
   ...
 
   return SQL_SUCCESS;
}

If you are familiar with C++ you can look at full source at codeplex.com. What this function does is it creates ODBC connection string, so basically it’s the same thing as using PDO_ODBC (no?). Both are implemented as extensions (not as PHP code) so there are no performance differences, test proves that.

After today’s analysis I can’t say which driver is better to use: ODBC or native driver. However, since Pdo driver is already being used in Zend Framework it’s easier and faster to use ODBC. Also, ODBC doesn’t require Sql PHP extension to be installed, so as long as you have Sql server and native client it will work without php.ini modifications.

In conclusion, if you want to use SQL Native driver with Zend Framework solutions are almost here. I can promise, that something stable and proven to be working by actual application will be released before middle of June. I would love to hear comments from Microsoft people or ODBC users – I’m confused a little bit, because I didn’t have a lot of experience with Microsoft’s Sql and ODBC (you can share find me in twitter also @juokaz).

To start with, Windows sometimes really annoys. For example, by default I can’t add files to C:\inetpub\wwwroot. It doesn’t ask for “Allow/Cancel?“, is doesn’t show permissions error – you just can’t do anything. I decided not to waste my time trying to find a way how to do it and ended up with virtual directory pointed to my project folder. I’m using Windows 7, so one can run programs as administrator, but having two Explorers is not a very good idea, especially when you can’t tell a difference between admin and non-admin mode (can you?).

First problem was routes – almost all frameworks nowadays uses something like “/controller/action/id” which is achieved by mod_rewrite and .htaccess. However, IIS is not Apache, hence .htaccess doesn’t exist. Although IIS has a routing module which pretty much works the same and also has nice a GUI for all who doesn’t know how to use regexp’s. Furthermore, it also has import function which surprisingly imports from .htaccess – select file, click Import, remove or fix not recognized rules and click Apply. I haven’t tried any complex rules, but since most of frameworks only require to redirect everything (“^.*$”) it should work.

Next “problem” is the database. MySQL works fine in Windows, but I wanted to use MSSQL. Not only because I haven’t tried MSSQL before, but also because MSSQL is much more integrated into Windows. However, MSSQL driver in PHP has some limitations. Nevertheless, Microsoft has released a native driver, which seems to have fixed all previous problems. You only need to download actual driver from here and PHP extensions from here. Extension can be used like this (it provides sqlsrv_* functions), however I really prefer using PDO or other object oriented database layer. That’s why I use it like this:

try {
    $hostname = "localhost\SQLEXPRESS";            //host
    $dbname = "zf-tutorial";            //db name
    $username = "sa";            // username like 'sa'
    $pw = "juozas";                // password for the user
 
    $dsn = "Driver={SQL Server Native Client 10.0};
            Server={$hostname};
            Database={$dbname};
            Uid={$username};
            Pwd={$pw};";
    $dbh = new PDO ("odbc:" . $dsn);
} catch (PDOException $e) {
    echo "Failed to get DB handle: " . $e->getMessage() . PHP_EOL;
    exit;
}
 
$sth = $dbh->prepare("SELECT * FROM albums");
$sth->execute();
 
$result = $sth->fetchAll();
print_r($result);

I should add, that I haven’t tested it much, but at least demo project from the tutorial works. Later this week I will probably choose which method to use (sqlsrv_* or PDO), because Zend framework currently doesn’t support MSSQL Native client and I will implement adapter myself (Zend_Db_Adapters are around 500 lines). Rob Allen is also working on a driver implementation for Zend so one of us should come with a solution pretty soon. Currently I’m using Zend_Db_Adapter_Pdo_Odbc from here, however it still works only as a hack.

That’s all – your Zend Framework project should work (you may also need to set correct file permissions).

If I wouldn’t have started Winphp competition, I may have never realized how Microsoft is struggling to support PHP. Starting from blogs and ending with special drivers, tutorials and even competitions. Is Microsoft trying to “repair” its public profile?