Event Code

Hello and thanks in advance;
I write this code that works fine out of PHPRunner, but when I insert in PHPRunner we have problem with WHILE sentence
Can you help me? I don´t Know what´s happen!
// Read de data

$rs = db_query("select * from " .$tablaDestino, $conn );
if($data=db_fetcharray($rs))

{

$camposDestino ="(";

echo($camposDestino ."
");

// Select de name o fields

$i=1
//SENTECES WITH PROBLEMS!!!____

while ( $i < mysql_num_fields($rs))

{

$camposDestino .= mysql_field_name($rs, $i) .", ";

$i = $i + 1;

}
//-----------------------------------------------------------------------------
echo($camposDestino ."
");
'Thanks