I haven't install pear in my PC,instead I download the packages and unzip them to "libs" dictionary in my web-app.the structure of dictionary of my web-app is roughly like this:
web-app +-/backend +-/libs +-/peardb +-pear.php +-pear5.php +-mdb2.php +-/mdb2
The application works fine in my two PCs,but throws "Cannot redeclare class mdb2_error" error while it running in virtual host.