How to set default style of layer using rest api in Geoserver

I want to change the default style of the layer in Geo server using the REST API.

For this i have this code:

  curl -v -u admin:geoserver -XPUT -H "Content-type: text/xml"
  -d polygon"
  http://mindcrewgis.com/geoserver/rest/layers/pymble:pymble_water

when run this command it is working fine form me. But when i convert this command in PHP then it is not working for me My PHP code for above curl command is

    $url="http://mindcrewgis.com/geoserver/rest/layers/pymble:pymble_water";
    $contentType = 'text/xml';
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_USERPWD, "myusername:mypassword"); 

     $data="
            
            polygon
            

            ";
     curl_setopt($ch, CURLOPT_PUT, true);
     curl_setopt($ch, CURLOPT_HTTPHEADER, 
                array("Content-Type: $contentType",
                'Content-Length: '.strlen($data))
            );
        curl_setopt($ch, CURLOPT_POSTFIELDS, $data);    
        curl_setopt($ch, CURLOPT_HEADER, false);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);


        $rslt = curl_exec($ch);

       $info = curl_getinfo($ch);

?> 

But this code is not working for me . There is something wrong in execute curl using PHP.