Data Types with Stream Support Using the SQLSRV Driver
Retrieving data as a stream is only available in the SQLSRV driver of the Microsoft Drivers for PHP for SQL Server, and is not available in the PDO_SQLSRV driver.
The following SQL Server data types can be retrieved as streams with the SQLSRV driver:
binary
char
image
nchar
ntext
nvarchar
text
UDT
varbinary
varchar
XML