Actually, the solutions is to open the php.ini file edit the include_path line and either completely change it to
include_path='.:/usr/share/php:/usr/share/pear'
or append the
'.:/usr/share/php:/usr/share/pear'
to the current value of include_path.
It is further explained in : http://pear.php.net/manual/en/installation.checking.php#installation.checking.cli.phpdir