สอบถามเรื่อง ฟังก์ชั่น php ทำงานกับ ฐานข้อมูล SQL Server (SQLSRV) Driver API

<?php
/*Connect to the local server using Windows Authentication and
specify the AdventureWorks database as the database in use. */
$serverName = "(local)";
$connectionInfo = array( "Database"=>"AdventureWorks");
$conn = sqlsrv_connect( $serverName, $connectionInfo);
if( $conn === false )
{
     echo "Could not connect.\n";
     die( print_r( sqlsrv_errors(), true));
}

/* Set up and execute the query. Note that both ReviewerName and
Comments are of SQL Server type nvarchar. */
$tsql = "SELECT ReviewerName, Comments 
         FROM Production.ProductReview
         WHERE ProductReviewID=1";
$stmt = sqlsrv_query( $conn, $tsql);
if( $stmt === false )
{
     echo "Error in statement preparation/execution.\n";
     die( print_r( sqlsrv_errors(), true));
}

/* Make the first row of the result set available for reading. */
if( sqlsrv_fetch( $stmt ) === false)
{
     echo "Error in retrieving row.\n";
     die( print_r( sqlsrv_errors(), true));
}

/* Note: Fields must be accessed in order.
Get the first field of the row. Note that no return type is
specified. Data will be returned as a string, the default for
a field of type nvarchar.*/
$name = sqlsrv_get_field( $stmt, 0);
echo "$name: ";

/*Get the second field of the row as a stream.
Because the default return type for a nvarchar field is a
string, the return type must be specified as a stream. */
$stream = sqlsrv_get_field( $stmt, 1, 
                            SQLSRV_PHPTYPE_STREAM( SQLSRV_ENC_CHAR));
while( !feof( $stream ))
{ 
    $str = fread( $stream, 10000);
    echo $str;
}

/* Free the statement and connection resources. */
sqlsrv_free_stmt( $stmt);
sqlsrv_close( $conn);
?>