int mysql_affected_rows ([int link_identifier])
mysql_affected_rows() returns the number of rows affected by the last INSERT, UPDATE or DELETE query on the server associated with the specified link identifier. If the link identifier isn't specified, the last opened link is assumed.
If the last query was a DELETE query with no WHERE clause, all of the records will have been deleted from the table but this function will return zero.
This command is not effective for SELECT statements, only on statements which modify records. To retrieve the number of rows returned from a SELECT, use mysql_num_rows().