finding children in php simplexml xpath

问题

I am running an xpath query on an xml stream and retreiving a set of data. In that i need to find the tag name. But im not able to find the way to retrieve the tag name. The xml stream is

<Condition> 
          <Normal dataItemId="Xovertemp-06" timestamp="2011-09-02T03:35:34.535703Z" name="Xovertemp" sequence="24544" type="TEMPERATURE"/> 
          <Normal dataItemId="Xservo-06" timestamp="2011-09-02T03:35:34.535765Z" name="Xservo" sequence="24545" type="LOAD"/> 
          <Normal dataItemId="Xtravel-06" timestamp="2011-09-02T03:35:34.535639Z" name="Xtravel" sequence="24543" type="POSITION"/> 
</Condition>

I am trying to parse this as

Temperature = Normal
Load - Normal

So what i did is

foreach ($xml->xpath("//n:Condition")->children("n") as $child) {
    echo $child["type"] . "="  . $child->getName();
}

I am getting the followin error

Fatal error: Call to a member function children() on a non-object in C:\xampp\htdocs\DataDumper\datadumper\test.php on line 53

Now i know this has got something to do with the way i query the xpath or something and i tried various combination such as adding an * slash to the query but the same error every time.

回答1:

Not sure why you used namespace notaion in the first place(the sample xml is not namespaced)

In your xpath, you need to select all condition/normal tags, not the condition tag as you were doing... Also, xpath() returns a list, so foreach over it. You don't need to access it as children, unless you want to parse the children of $child. There it would make sense, and it would work as expected.

foreach ($xml->xpath("/Condition/Normal") as $child) {
    echo $child["type"] . "="  . $child->getName()."<br/>";
}

outputs

TEMPERATURE=Normal
LOAD=Normal
POSITION=Normal

回答2:

The problem is due to SimpleXMLElement::xpath() returning an array and not a SimpleXMLElement. I'm also not sure about the namespace support in the XPath query however I'm sure you can fiddle with that to work it out. In any case, I see no n namespace in your XML.

The answer really depends on how many elements you expect to match your XPath query. If only one, try

$conditions = $xml->xpath('//Condition');
if (count($conditions) == 0) {
    throw new Exception('No conditions found');
}
$condition = $conditions[0];
foreach ($condition->children() as $child) {
    printf('%s = %s', (string) $child['type'], $child->getName());
}

来源：https://stackoverflow.com/questions/7279638/finding-children-in-php-simplexml-xpath

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php

xml

xpath

simplexml