php怎么给xml节点添加属性值？

$xml =<<<EOT

<?xml version="1.0"?>

<root>

<section name="Section1">

<category id="Category1" name="google">

</section>

</root>

EOT

$objXML=simplexml_load_string($xml)

$objXML->section->addAttribute('city', 'abc')

echo $objXML->asXML()

$xml =<<<EOT

<?xml version="1.0"?>

<root>

<section name="Section1">

<category id="Category1" name="google">

</section>

</root>

EOT

$objXML=simplexml_load_string($xml)

$objXML->section->addAttribute('city', 'abc')

echo $objXML->asXML()

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