You could always change the error reporting options in PHP :) Since these seem to be warnings and not actual errors (the application will still run, will it not?). Jump to php.ini and edit the
error_reporting line.
If you do something like
error_reporting = E_ALL ^ E_DEPRECATED
you won't be seeing these warnings anymore. Although I really don't recommend it as a permanent solution. The best thing is to upgrade the application (or downgrade php again? or maybe run two instances of php?)