mysql loop problem

Hi, I am trying to write some code to sit and wait for an entry in a table, once an entry is made it is processed and then the waiting loop begins again. Problem is that after a period of time the code just stops, almost like a timeout with no error message or any indication of why. This is the code: echo('Waiting for command \n'); do { $result = mysql_query("SELECT * FROM command_queue LIMIT 1"); $rows = mysql_num_rows($result); } while ($rows == 0); My PHP version is 4.2.3. Does anyone have any idea why this is occurring? Is there maybe a better way of doing this? Any help will be much appreciated. Gareth