passing JVM options when using php Java extension?

Hi,
I managed to get the Java extension working on php 4.3.10 after following
various bits of advice from
http://www.thelinuxpimp.com/main/mod...rticle&sid=419
and http://uk.php.net/java

I have some Java code which runs fine from Java at the command line when
specifying certain JVM options -Xmx and -Xms. I am now calling this class
from php but can't see any way of pasing the arguments to the JVM created
from the php process. Is there something in the jre or php.ini that I can
edit to force these options, or is it hidden somewhere in the java extension
source?

Any suggestions appreciated.
TIA,
S.