Possible to prevent a virtualhost or etc.. to use exec() or...?

I'm running a linux apache server 1.3.26 with php 4.2.2 I have some virtualhosts on my server my mainserver is: www.!!!!!!.com and they are hl.!!!!!!.com ... for ex: i don't want any php code to be able to run exec() or system() command which is being ran on hl.!!!!!!.com http://hl.!!!!!!.com/testing.php <--------- if he has something like system(...) or etc.. i want to php script to exit or deny BUT! Only for hl subdomain. And i don't want him to be able to include read fopen etc... files which are not in his home tree... for ex: he shouldn't be able to fopen /usr/local/apache/logs/error_log <------ This is just an example, please don't tell me to do chown root error_log This is just an example i just want to make seperate access files... permissions for php for specified accounts.. Is this possible? or? I'm looking for your response. Kind Regards.