Do you have shell access? If so try 'which php'.
Else if you run phpinfo() it will show you a lot of into, not sure it it shows the path directly but I do know it shows the ini file locations from which you can usually dervive the path as being ../bin/php file that location. Also look at the --prefix option if any in the configure command it outputs. If there is one that will give you the path to append to bin/php
else it is /usr/local/bin/php
Also there does not have to be a path to php, it can be build in such a way that it is built into the webserver.