PHP program running from shell ends silently

Hi: I'm running a 'batch' PHP program from the shell with "#!/usr/bin/php -q" as the first line. After some processing, it ends silently without any visible notice or error. It processes information from a PostgreSQL database and shows its progression (via echoes) until it suddenly stops. This behaviour occurs when it treats a high volume of information, with just a few records it works fine. I guess it may be a problem of lack of memory but I have tried to look for any trace in /var/logs and I cannot find any sign of the program. How can I know what is happening? Where can I look for the error? Thanks a lot!