How to detect version of PHPUnit

I'm writing unit tests using an older version of PHPUnit (3.4) and thus can't use all supported assertions listed in manual of 3.5 and 3.6. Though I could reengineer tests for instant support in my environment here, I'd like to make my tests dependent on current version of PHPUnit, so that it's using assertsInstanceOf() as soon as my or any other one's testing environment is providing PHPUnit 3.5+.I'm writing unit tests using an older version o