Требования
  
   Requirements for Win32 platforms.
  
  
   The extension requires the MS SQL Client Tools to be installed
   on the system where PHP is installed. The Client Tools can
   be installed from the MS SQL Server CD or by copying
   ntwdblib.dll from 
   \winnt\system32 on the server to
   \winnt\system32 on the PHP box.
   Copying ntwdblib.dll will only provide access
   through named pipes.
   Configuration of the client will require installation of all the tools.
  
  
   Requirements for Unix/Linux platforms.
  
  
   To use the MSSQL extension on Unix/Linux, you first need to build and 
   install the FreeTDS library. Source code and installation instructions 
   are available at the FreeTDS home page: 
   » http://www.freetds.org/
  
  Замечание: 
   
    On Windows, the DBLIB from Microsoft is used. Functions that return a
    column name are based on the dbcolname() function 
    in DBLIB.  DBLIB was developed for SQL Server 6.x where the max
    identifier length is 30.  For this reason, the maximum column length 
    is 30 characters.  On platforms where FreeTDS is used (Linux), this is
    not a problem.
   
  
  Замечание: 
   
    On Windows, if you're using MSSQL 2005 or greater you must copy the 
    ntwdblib.dll into the directory where you have 
    installed php and overwrite the one thats already in there. This is 
    due to the version distributed is  old and outdated. Alternatively you 
    can use the ODBC, 
    PDO_DBLIB or 
    PDO_ODBC extensions, to talk to MSSQL.