syntax error

a system with php4 and mysql 4.x I had these lines:

require("/db-config"); // includes $dbhost, $buname, $dbpass
$db = mysql_connect($dbhost, $dbuname, $dbpass);
mysql_select_db($dbname,$db);

$sql = "SELECT * FRM CATEGRY WHERE ";
$result = mysql_query($sql,$db);
$num=mysql_num_rows($result);
while ($myrow = mysql_fetch_array($result)) {


Moving the *.php to a php5 and mysql 5.x site I get these errors:

PHP Warning: mysql_num_rows(): supplied argument is not a valid MySQL
result resource in
PHP Warning: mysql_fetch_array(): supplied argument is not a valid MySQL
result resource in


Looking at the manual, I cannot see what I am doing wrong.

bye

R.