How do I find out which version of Doctrine I am running?

Check out the file lib/Doctrine/ORM/Version.php, there is a constant in there that shows the version. It's also accessible from a running app but this is easier.

If you are using the composer to handle dependencies on your project, then you should try with:

php composer.phar show --installed

OR

php composer.phar show -i | grep doctrine

And the output will be something like:

doctrine/annotations                     v1.1.2             Docblock Annotations Parserdoctrine/cache                           v1.3.0             Caching library offering an object-oriented API for many cache backendsdoctrine/collections                     v1.2               Collections Abstraction librarydoctrine/common                          v2.4.1             Common Library for Doctrine projectsdoctrine/data-fixtures                   v1.0.0             Data Fixtures for all Doctrine Object Managersdoctrine/dbal                            2.3.4              Database Abstraction Layerdoctrine/doctrine-bundle                 v1.2.0             Symfony DoctrineBundledoctrine/doctrine-fixtures-bundle        v2.2.0             Symfony DoctrineFixturesBundledoctrine/inflector                       v1.0               Common String Manipulations with regard to casing and singular/plural rules.doctrine/lexer                           v1.0               Base library for a lexer that can be used in Top-Down, Recursive Descent Parsers.doctrine/orm                             2.3.5              Object-Relational-Mapper for PHP

Within my symfony2 and symfony3 project, the path to find the correct Version.php file, line 39, was:

Vendor/doctrine/orm/lib/Doctrine/ORM/Version.php