Anybody got a way of accessing the path to the firebird directory from PHP?

I am trying to tidy up the installer on Tikipro and have a single
niggle. I need to run isql to create the blank database and currently I
have the path hard coded for my system. Obviously I'd like to replace
that with something that does not need changing for windows/unix and
different setups.

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Lester Caine
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L.S.Caine Electronic Services