allsections.xml

<?xml version="1.0"?>
<config>
    <all>
        <hostname>all</hostname>
        <name>thisname</name>
        <db>
            <host>127.0.0.1</host>
            <user>username</user>
            <pass>password</pass>
            <name>live</name>
        </db>
        <one>
            <two>
                <three>multi</three>
            </two>
        </one>
    </all>

    <staging extends="all">
        <hostname>staging</hostname>
        <db>
            <name>dbstaging</name>
        </db>
        <debug>false</debug>
    </staging>

    <other_staging>
        <only_in>otherStaging</only_in>
        <db>
            <pass>anotherpwd</pass>
        </db>
    </other_staging>


</config>