To use the pthreads module in the browser with WAMP Server you need to copy the "pthreadVC2.dll" into the apache "bin" directory also.
You should now have he "pthreadVC2.dll" in both of these folders (if installed in default location):
C:\wamp\bin\php\php[x.x.xx]\bin
C:\wamp\bin\apache\apache[x.x.x]\bin
You will also need to update the php.ini file within the php bin directory and the apache bin directory to include:
extension=php_pthreads.dll