Help connecting with oracle

["Barreira, Sergio" <webmaster_dgr@entrerios.gov.ar>]

Hi: 
      I have a Oracle 7.3.3 on Unix, but in my computer (client) Windows
2000 i have a php source code that try to connect with this database.
      I test with TNSPING and SQLPLUS commands line, and connect with both
susseffuly, but when i try to connect with php can't. 
      I have a Apache server with php 4.2.2 
   
      i'm trying the follow code:
 
 <? 
if ($conn=Ora_Logon(" webmaster@PROD <mailto:webmaster@PROD> ",
"webmaster")) {
        echo "<B>SUCCESS ! Connected to database<B>\n";
} else {
        echo "<B>Failed :-( Could not connect to database<B>\n";
}
Ora_Logoff($conn);
 
?>

And the error is:

Warning: Oracle: Connection Failed: in C:\FoxServ\www\conectar.php on line 2
Failed :-( Could not connect to database 
Warning: ora_logoff(): supplied argument is not a valid Oracle-Connection
resource in C:\FoxServ\www\conectar.php on line 7
 
 
Help!!