This extension is to show low level PHP structures. It is therefore very sensitive to changes in the PHP API. If the PECL install doesn't work, please try the latest version from GitHub:
git clone https://github.com/derickr/vld.git cd vld phpize ./configure make && make install
If it still doesn't compile, then VLD is not for you. Patches are welcome through Pull Requests.
There are a few options in the form of php.ini settings available.
In order for VLD to do anything, you need to set vld.active=1.
If you want to prevent VLD from executing code, set vld.execute=0.
Other settings are also available, but not documented yet.
Please see the project page at http://derickrethans.nl/projects.html#vld for some more information.