PUT string of data to XML server using PHP

// Start curl  
    $ch = curl_init();  
// URL for curl  
    $url = "http://example.appspot.com/examples";  

// Put string into a temporary file  
    $putString = '<client>the RAW data string I want to send</client>';

/** use a max of 256KB of RAM before going to disk */  
    $putData = fopen('php://temp/maxmemory:256000', 'w');  
    if (!$putData) {  
        die('could not open temp memory data');  
    }  
fwrite($putData, $putString);  
fseek($putData, 0);  

// Headers  
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);  
// Binary transfer i.e. --data-BINARY  
curl_setopt($ch, CURLOPT_BINARYTRANSFER, true);  
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);  
curl_setopt($ch, CURLOPT_URL, $url);  
// Using a PUT method i.e. -XPUT  
curl_setopt($ch, CURLOPT_PUT, true);  
// Instead of POST fields use these settings  
curl_setopt($ch, CURLOPT_INFILE, $putData);  
curl_setopt($ch, CURLOPT_INFILESIZE, strlen($putString));  

$output = curl_exec($ch);  
echo $output;  

// Close the file  
fclose($putData);  
// Stop curl  
curl_close($ch);  

since I haven't worked with cURL so far I can't really answer to that topic. If you'd like to use cURL I'd suggest looking at the server log and see what actually didn't work (so: Was the output of the request really what it's supposed to be?)

If you don't mind switching over to another technology/library I'd suggest you to use the Zend HTTP Client which is really straight forward to use, simple to include and should satisfy all your needs. Especially as performing a PUT Request is as simple as that:

<?php 
   // of course, perform require('Zend/...') and 
   // $client = new Zend_HTTP_Client() stuff before
   // ...
   [...]
   $xml = '<yourxmlstuffhere>.....</...>';
   $client->setRawData($xml)->setEncType('text/xml')->request('PUT');
?>

Code sample is from: Zend Framework Docs # RAW-Data Requests

Another way to add string body to the PUT request with CURL in PHP is:

 <?php
        $data = 'My string';
        curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'PUT'); // Define method type
        curl_setopt($ch, CURLOPT_POSTFIELDS, $data); // Set data to the body request
  ?>

I hope this helps!