Problem of unicode ( Inserted data / Query )

Dear You, How to control php convert inserted data or query to / from MS-SQL ( MUST in charset of unicode ) ? For example, Insert data into MS-SQL : A client user ( using his/her own language ) insert some data into MS-SQL, then MS-SQL MUST store the data ( which come from the client user ) in unicode format ( charset ). Query from MS-SQL : A client user ( using his/her own language ) search some info from MS-SQL, but all of the format of stored data were unicode ( charset ), so must convert the charset of unicode to a special format ( charset ) for the client user ( correspond to his/her own language ) Many thank for your help so much ! Best Regards, Edward.