in //PEAR/HTTP/Session/Session.php such piece of code could be found:

    $container_class = 'HTTP_Session_Container_' . $container;
    $container_classfile = 'HTTP/Session/Container/' . $container . '.php';
    require_once $container_classfile;

the page silently dies on the 'require_once' statement, which is perfectly ok without xdebug.

when I tried to force it to evaluate the string before passed to the statement, it worked well:
require_once "$container_classfile";