added a sqlsrv test, a variant

test/pdo_sqlsrv/pdo_308_empty_output_param.phpt

@@ -1,5 +1,7 @@
 --TEST--
 GitHub issue #308 - empty string set to output parameter on stored procedure 
+--DESCRIPTION--
+Verifies GitHub issue 308 is fixed, empty string returned as output parameter will remain an empty string.
 --SKIPIF--
 --FILE--
 <?php

test/sqlsrv/srv_308_empty_output_param.phpt

@@ -0,0 +1,47 @@
+--TEST--
+GitHub issue #308 - empty string set to output parameter on stored procedure 
+--DESCRIPTION--
+A variation of the example in GitHub issue 308 is fixed. A NULL value returned as output parameter will remain as NULL.
+--SKIPIF--
+--FILE--
+<?php
+require_once("tools.inc");
+
+require_once("autonomous_setup.php");
+
+// Connect
+$conn = sqlsrv_connect($serverName, $connectionInfo) ?: FatalError("Failed to connect");
+
+$procName = GetTempProcName();
+
+$sql = "CREATE PROCEDURE $procName @TEST VARCHAR(200)='' OUTPUT
+AS BEGIN
+SET NOCOUNT ON;
+SET @TEST=NULL;
+SELECT HELLO_WORLD_COLUMN='THIS IS A COLUMN IN A SINGLE DATASET';
+END";
+$stmt = sqlsrv_query($conn, $sql);
+if ($stmt === false) { FatalError("Failed to create stored procedure"); }
+
+$sql = "EXEC $procName @Test = ?";
+$out = '';
+
+$param = array(array(&$out, SQLSRV_PARAM_INOUT));
+$stmt = sqlsrv_query($conn, $sql, $param);
+if ($stmt === false) { FatalError("Failed to execute stored procedure"); }
+
+$result = sqlsrv_fetch_array($stmt, SQLSRV_FETCH_NUMERIC);
+sqlsrv_next_result($stmt);
+
+echo "OUT value: ";
+var_dump($out);
+
+// Free statement and connection resources
+sqlsrv_free_stmt($stmt);
+sqlsrv_close($conn);
+
+print "Done";
+?>
+--EXPECT--
+OUT value: NULL
+Done