I reviewed the LimeSurvey code about the database driver implementation; Actually the used framework already supports the pdo_dblib driver. The adaptations that should be made for pdo_dblib to work are already made for pdo_sqlsrv and require only a small extension for these statements. As proof-of-principle I adapted Limesurvey 2.00 plus (build 130611) to work with pdo_dblib. Adapted files are uploaded in a ZIP-file. The adapted lines are recognizable by comments “// ADAPTED JV”. In my adaptations I assume DBLIB is always used to connect a MS SQL-server database, though the driver can theoretically support other databases. I used DBLIB in combination with the FreeTDS driver.

Hope this helps to get pdp_dblib supported in the next LimeSurvey versions.

Furthermore I saw that not always proper SQL coding is used in the create statements specific for MS SQL-server; sometimes no “NULL” is used in the column specification. Data type “TEXT” is deprecated since SQL server 2005. Adapted files are also attached in the same ZIP.

I actually also tried getting LimeSurvey to work with pdo_odbc. The Yii framework doesn't support pdo_odbc by default. As you adapt Yii to use MssqlSchema for odbc driver, you still have the problem that pdo_odbc doesn't function with parameter binding, which makes it useless for LimeSurvey.

@joop: Thank you for your effort. I completely overlooked the attached patch, so sorry! I will check it and let you know.

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=13050

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=13062

joop, thank you. I did a few minor changes but in general your patch helped a great deal. This will be available in the next 2.0+ build.

Fix committed to 2.05 branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=13064

2.00+ Build 121009 released

There is still a small bug in InstallerController.php at line 297. The installation will not work if you have an empty database, while using dblib.
The assumption that $this->connection->createCommand()->select()->from('{{surveys}}')->queryAll(); will throw an error is not true with MSSQL. It will just return an empty result set, so the catch is never reached and bTablesDoNotExist will not be set to true (and no tables will be populated).
I think using a row count query like I used in my patch will solve the problem.

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=13307

Thank you for the hint!

Fix committed to 2.05 branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=13309

Version 2.00+ Build 131022 released.