clarification on core modules

Guys, I"ve recently installed php 5.6.5 for a client. And he specifically requested both mail and pdo modules to be enabled. However when I went to installed them, I found that each was now a part of core php. When the client logged into the system and did a php -m and grepped for those modules he didn't see them. So my question is a rather basic one. If a module has been included in core, should we expect to see it listed in the output of php -m? Thanks Tim -- GPG me!! gpg --keyserver pool.sks-keyservers.net --recv-keys F186197B