ssh plus svn through php

I am trying to run the following command through php:

exec("svn export svn+ssh://svn@XXXXXX/var/svn/XXXX $OUTPUT/$value2");

But it asks for my password each time. I have a key stored on the svn server, how c开发者_如何学Goan I pass pass my private key to this script to use?

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is the key which is stored in the server under the user whom is running that script?

IE normally when you log in you're logged in as "bob". However when PHP is executed, it's executed as WWW; make sure the key is stored for the proper user.