XML : How to request only particular fields from an XML output?

I have an access key to an API, which allows me to obtain data about products (such as price, description, etc).

I am aware of 2 manual ways to use this key:

1) Use the "modify headers" firefox addon, insert the key in the headers, and then type the URL that will yield an XML file (https://api.domain.com/search?parameter=something), and I will see an output tree like this:

  <manufacturer-name>SONY</manufacturer-name>    <price>99.99</price>    

Along with another 20 fields.

2) Use PHP file with this code:

  $myHeaders = array("key: code");    $ch = curl_init();    curl_setopt($ch, CURLOPT_URL, "https://api.domain.com/search?parameter=something");  curl_setopt($ch, CURLOPT_HTTPHEADER,$myHeaders);  curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);  curl_setopt($ch, CURLOPT_HEADER, 0);    $returnResult = curl_exec($ch);    if ($returnResult) {      //parse HTTP Body to determine result of request      if (stripos($returnResult,"Error Code ")) {          // error occurred          trigger_error($returnResult,E_USER_ERROR);      }      else{          // success          echo $returnResult;      }  }    else{      // connection error      trigger_error(curl_error($ch),E_USER_ERROR);  }    curl_close($ch);    

And then I see this output:

SONY 99.99

My question:

Using same PHP code, how can I request only the price field to show up?

(I ask this because later on, I will want my server to make auto requests like this, and update my own database with the current values of these fields).