SimpleXML用PHP选择属性？

Question

Okay so I've never worked with SimpleXML before and I'm having a few problems

Here's my PHP:

map.api.php

$location = $_SESSION['location'];
$address = $location; // Business Location
$prepAddr = str_replace(' ','+',$address);
$feedUrl="http://nominatim.openstreetmap.org/search?q=". $prepAddr ."&format=xml&addressdetails=1&polygon=1";

$sxml = simplexml_load_file($feedUrl);

foreach($sxml->attributes() as $type){
  $lat = $type->place['lat'];
  $long = $type->place['lon'];
}

And here's an example of the XML table I'm working from.

<searchresults timestamp="Thu, 28 Jan 16 14:16:34 +0000" attribution="Data © OpenStreetMap contributors, ODbL 1.0. http://www.openstreetmap.org/copyright" querystring="M27 6bu, 149 Station road, Swinton, Manchester" polygon="true" exclude_place_ids="65827001" more_url="http://nominatim.openstreetmap.org/search.php?format=xml&exclude_place_ids=65827001&accept-language=en-US,en;q=0.8&polygon=1&addressdetails=1&q=M27+6bu%2C+149+Station+road%2C+Swinton%2C+Manchester">
  <place place_id="65827001" osm_type="way" osm_id="32861649" place_rank="26" boundingbox="53.5122168,53.5190893,-2.3402445,-2.3331231" lat="53.5156919" lon="-2.3368185" display_name="Station Road, Newtown, Salford, Greater Manchester, North West England, England, M27 4AE, United Kingdom" class="highway" type="secondary" importance="0.5">
    <road>Station Road</road>
    <suburb>Newtown</suburb>
    <town>Salford</town>
    <county>Greater Manchester</county>
    <state_district>North West England</state_district>
    <state>England</state>
    <postcode>M27 4AE</postcode>
    <country>United Kingdom</country>
    <country_code>gb</country_code>
  </place>
</searchresults>

I want to select the " lat " and " lon " attributes from < place >, but when I echo $lat and $long they are empty, why?

Answer 1

When you call attributes as you did above, it's only going to act on the first element, which in your case is the root. You need to call attributes on the element you want the attributes for. Easiest way to do that would be

$sxml->place[0]->attributes()

Does that make sense? Basically you're telling SimpleXML to seek to the element you want to analyze, then returning a new SimpleXML object that represents that element's attributes. See if the docs help

Another option you have is using xpath to return all place elements, then iterating through those and calling attributes() on each element, in the case where you have more than one place.

Answer 2

Okay so I fixed this myself.

Instead of running everything through the foreach loop (as shown below):

foreach($sxml->attributes() as $type){
 $lat = $type->place['lat'];
 $long = $type->place['lon'];
}

I just directly got the attribute values and stored them in a variable:

$lat = $sxml->place->attributes()->lat;
$long = $sxml->place->attributes()->lon;

This then returned an error/warning: Warning: main() [function.main]: Node no longer exists

By using isset and checking if the value exists first, you can get around this.

if (isset($sxml->place))
{
 $lat = $sxml->place->attributes()->lat;
 $long = $sxml->place->attributes()->lon;
}