Problem in getting the table name

[admin]

I have wrote some code in PHP using ODBC to display all the Table name in Access mdb
<?
$db= odbc_connect ("mobile", "","");
$result = odbc_tables($db);
odbc_result_all($result);
?>
This code will show all the information without any problem. but when I changed to code below, it crash the PHP.
<?
$db= odbc_connect ("mobile", "","");
$result = odbc_tables($db);
while (odbc_fetch_row($result)){
echo odbc_result($result,3);
}
?>
I am using apache + php 4.03 + winnt workstation.
I have no idea what is going on. anyone can help me?