Not all IDEs (actually, i haven’t seen even one IDE that does this), can run your unit-tests as soon as something changes.
Inspired by Greg Young’s Mighty Moose system, the following script runs inside a shell, will wait for changes in your PHP-files, and runs the corresponding unit-test as soon as something changes. It doesn’t run the WHOLE unit-tests suite, but merely the test that matches up the source file.
This script will assume that your test-directory matches the directory-structure of your source directories. Meaning: /src/foo/bar/baz.php will have its corresponding tests inside the file /tests/foo/bar/bazTest.php, which is common practice for your tests anyway.
Fork && have fun!