How does php determine whether to read the null value in mssql?

How does php determine whether to read the null values in mssql? Environment: linuxredhat5.4, php + freetds + mssql2005server //********************************* * ******************* $ value = iconv (& quot; how can I judge the null values in mssql read by php?
Environment: linux redhat 5.4, php + freetds + mssql 2005 server



//************************************** ***************

$ Value = iconv ("GB2312", "UTF-8", $ row [iconv ("UTF-8", "GB2312", $ field)]);
Echo""; // If $ field is null in mssql 2005, the following statement is not executed
Echo $ value; // if $ field is null in mssql 2005, the following statement is not executed

Echo""// If $ field is null in mssql 2005, the following statement is not executed




//****************************
Echo"
";
// Echo "waredatememo:". $ test ["waredatemo"];
Echo"
";
Echo iconv ("GB2312", "UTF-8", $ row [iconv ("UTF-8", "GB2312", $ field)]) or die ("MSG results :". mssql_get_last_message ());

$ Field is null in mssql 2005.

When the preceding statement is used for testing, the web page only displays: "MSG results:" without any message!

Solve it !....

------ Solution --------------------
Use empty to judge the query result! Because the result is an array, you cannot directly use = ''or = 0 to judge