php simplexml get a specific item based on the value of a field

Question

Is there a way i can get a specific item with SimpleXML ?

For example, i would like to get the title of an item having ID set to 12437 with this example xml :

Answer 1

You want to use Xpath for this. It's basically exactly the same as outlined in SimpleXML: Selecting Elements Which Have A Certain Attribute Value but in your case you're not deciding on an attribute value but on an element value.

However in Xpath for both the element you're looking for is the parent.So formulating the xpath expression is kind of straight forward:

// Here we find the item element that has the child  element
//   with node-value "12437".

list($result) = $data->xpath('(//items/item[id = "12437"])[1]');
$result->asXML('php://output');

Output (beautified):

  
  12437

So let's see the heart of this xpath query again:

//items/item[id = "12437"]

It's written as: Select all elements that are a children of any elements which on their own have a child element named with the value "12437".

And now with the missing stuff around:

(//items/item[id = "12437"])[1]

The parenthesis around says: From all these elements, pick the first one only. Depending on your structure this might or might not be necessary.

So here is the full usage example and online demo:

  
    
    43534
  
  
    
    12437
  
  
    
    7868
  

XML;

$data = new SimpleXMLElement($str);

// Here we find the item element that has the child  element
//   with node-value "12437".

list($result) = $data->xpath('(//items/item[id = "12437"])[1]');
$result->asXML('php://output');

So what you call a field in your questions title is by the book a child-element. Keep this in mind when searching for more complicated xpath queries that get you what you're looking for.