Description:
------------
---
From manual page: http://www.php.net/example.xml-structure
---
Example one that shows an example usage throws an undefined index. This is because when it first calls startElement, $depth[$parser] does not get initialised.
To fix this, I changed the startElement function to 
function startElement($parser, $name, $attrs)
{
    global $depth;
    if (isset($depth[$parser])) {
        for ($i = 0; $i < $depth[$parser]; $i++) {
            echo "  ";
        }
    } else {
        $depth[$parser] = 0;
    }
    echo "$name\n";
    $depth[$parser]++;
}
Would be good to add this improvement to the documentation.