In this new post to his Oracle blog, Chris Jones shows how to set up DBMS_OUTPUT to work with the OCI8 extension available for PHP.

Immediately after OOW, Alison and I have got straight into updating the Underground PHP & Oracle Manual. We've had our heads right down. [...] When reviewing the DBMS_OUTPUT section I tried using a PIPELINED PL/SQL function and found a significant speed improvement over the basic method.

He shows a few different methods for getting it working and includes both the code, SQL to create the functions and a bit of stats at the end showing which method is the fastest (the pipelined version wins out by quite a bit every time).