Description:
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I have been trying to get the last example at https://msdn.microsoft.com/en-us/library/ff628166(v=sql.105).aspx to work for the last two days.  The bindParam INPUT_OUTPUT variable never gets assigned when using the stored procedure.  I have verified that the stored procedure does indeed work when queried, PDO just fails to assign the variable.  Note this is an MsSQL server using dblib.



Test script:
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<?php
   $database = "AdventureWorks";
   $server = "(local)";
   $dbh = new PDO( "sqlsrv:server=$server ; Database = $database", "", "");

   $dbh->query("IF OBJECT_ID('dbo.sp_ReverseString', 'P') IS NOT NULL DROP PROCEDURE dbo.sp_ReverseString");
   $dbh->query("CREATE PROCEDURE dbo.sp_ReverseString @String as VARCHAR(2048) OUTPUT as SELECT @String = REVERSE(@String)");
   $stmt = $dbh->prepare("EXEC dbo.sp_ReverseString ?");
   $string = "123456789";
   $stmt->bindParam(1, $string, PDO::PARAM_STR | PDO::PARAM_INPUT_OUTPUT, 2048);
   $stmt->execute();
   print $string;   // Expect 987654321 but received 123456789

Expected result:
----------------
$string === "987654321"

Actual result:
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$string === "123456789"