sqlsrv_next_result() returns incorrect result with varchar(max) field when Always Encrypted is enabled

[yitam]

To reproduce this, connect with Always Encrypted enabled, create a table with only one varchar(max) column and then fetch the result by running two selects in a row. This is an example (the problem is gone when the column type is varchar(1024)):

$tableName = 'TextTable';
$sql = "create table $tableName (col1 varchar(max) COLLATE Latin1_General_BIN2 ENCRYPTED WITH (ENCRYPTION_TYPE = deterministic, ALGORITHM = 'AEAD_AES_256_CBC_HMAC_SHA_256', COLUMN_ENCRYPTION_KEY = AEColumnKey) )";

$stmt = sqlsrv_query($conn, $sql);

$sql = "insert into $tableName (col1) VALUES (?)";
$params = array("This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test This is a test ");

$stmt = sqlsrv_prepare($conn, $sql, $params);
if ($stmt) {
    $r = sqlsrv_execute($stmt);
    if (!$r) {
        print_r(sqlsrv_errors());
    }
}

$stmt = sqlsrv_prepare($conn, "SELECT * FROM [$tableName]; SELECT * FROM [$tableName]");
if ($stmt) {
    $r = sqlsrv_execute($stmt);
    if (!$r) {
        print_r(sqlsrv_errors());
    }
}

echo "1. next result? ";
$next = sqlsrv_next_result($stmt);
var_dump($next);

$row = sqlsrv_fetch($stmt);
if ($row) {
    $fld = sqlsrv_get_field($stmt, 0, SQLSRV_PHPTYPE_STRING(SQLSRV_ENC_CHAR));
    echo(substr($fld, 0, 15)) . PHP_EOL;
}

echo "2. next result? ";
$next = sqlsrv_next_result($stmt);
var_dump($next);

echo "3. next result? ";
$next = sqlsrv_next_result($stmt);
var_dump($next);

The expected output is

1. next result? bool(true)
This is a test
2. next result? NULL
3. next result? bool(false)

The actual output is

1. next result? bool(true)
This is a test
2. next result? bool(true)
3. next result? NULL

[yitam]

Fixed in 5.1.2-preview