如果节点存在Xpath，则修改属性？

Question

I'm trying to modify a node attribute if the node exist or create it if not in a xml file using Xpath. xml file looks like that :

<krpano>
    <hotspot name="hs1" ath="0" atv="0"/>
    <hotspot name="hs2" ath="0" atv="0"/>
</krpano>

and here is my php code :

<?php
$str_json = file_get_contents('php://input');
$json_data = json_decode($str_json);

$file = 'myxmlfile.xml';
$xml = simplexml_load_file($file);
$krpano = $xml->xpath("//krpano");
$hotspot = $xml->xpath('//hotspot[@name="'.$json_data->name.'"]');

if ($hotspot){
    $xml->xpath('//hotspot[@name="'.$json_data->name.'"]/@ath->'.$json_data->xpos.'');
    $xml->xpath('//hotspot[@name="'.$json_data->name.'"]/@atv->'.$json_data->ypos.'');
}else{
    $newhs = $krpano[0]->addChild('hotspot');
    $newhs->addAttribute('name', $json_data->name);
    $newhs->addAttribute('ath', $json_data->xpos);
    $newhs->addAttribute('atv', $json_data->ypos);
}

$xml->asXML($file);

?>

if the node doesn't exist then it's added, no problem, but if it exist the attribute values aren't changed.

Answer 1

You can't alter attributes like that with XPath,

$xml->xpath('//hotspot[@name="'.$json_data->name.'"]/@ath->'.$json_data->xpos.'');
$xml->xpath('//hotspot[@name="'.$json_data->name.'"]/@atv->'.$json_data->ypos.'');

you just need to modify them directly from the hotspot you already have...

$hotspot[0]['ath'] = $json_data->xpos;
$hotspot[0]['atv'] = $json_data->ypos;