the pecl-pam homepages only states, that "PHP 4.3.0 or newer" is required. so would it be possible to at PHP_TARGETS for 5.4 and 5.5?
Unfortunately not. It has not had an update since 2009, so it will probably be removed from the tree sometime soon.
Is this justified? It's a quite simple program, and it is working as intended. Also with php-5.5 (just tested).