Display array variable from SimpleXML

I have a very simple XML file:

<?xml version="1.0" encoding="ISO-8859-1"?>
<Data><Day Num="4197">
<Date>270611</Date>
<Energy>47</Energy>
</Day>
<Day Num="4219">
<Date>190711</Date>
<Energy>202</Energy>
</Day>
<Day Num="4220">
<Date>200711</Date>
<Energy>17074</Energy>
</Day>
<Day Num="4221">
<Date>210711</Date>
<Energy>11563</Energy>
</Day>
<Day Num="4222">
<Date>220711</Date>
<Energy>18178</Energy>
</Day>
<Day Num="4223">
<Date>230711</Date>
<Energy>24916</Energy>
</Day>
<Day Num="4224">
<Date>240711</Date>
<Energy>10555</Energy>
</Day>
<Day Num="4225">
<Date>250711</Date>
<Energy>12683</Energy>
</Day>
</Data>

With some help on here yesterday I got it to pull out Date and Energy, but now I want to display Day Num.

I did a print_r($xml); which shows:

   SimpleXMLElement Object
(
    [Day] => Array
        (
            [0] => SimpleXMLElement Object
                (
                    [@attributes] => Array
                        (
                            [Num] => 4197
                        )

                    [Date] => 270611
                    [Energy] => 47
                )

            [1] => SimpleXMLElement Object
                (
                    [@attributes] => Array
                        (
                            [Num] => 4219
                        )

                    [Date] => 190711
                    [Energy] => 202
                )

So the Num field I want is in an array, but I cannot figure out how to extract it?

My current code is very simple, it is:

$xml = simplexml_load_file("DATA.XML");


foreach($xml->children() as $day开发者_如何学运维)
{
    list($date, $energy) = $day->children();
    echo ',Date: ' . $date . ', Energy: ' . $energy . '<br />';
}

How would I extract Day Num please?

Use: $day->attributes()->Num

See: SimpleXMLElement::attributes for further reading.