Mini REST client and server

REST is used in the project I am working on. The two libraries REST and CURL are used in the project. This is the client and server that I simplified after research. Please correct me

mini_rest_call.php client
rest_server.php server end

/**
 * mini REST call
 *
 * @param mixed $url REST server-side URL
 * @param mixed $method method
 * @param array $params parameters
 * @param mixed $request request method (get, post, put, delete)
 * @param mixed $request return format (json, xml)
 *
 * @author PiscDong (http://www.piscdong.com/)
*/
function mini_rest_call($url, $method='', $params=array(), $request='get', $format='json' ){
 if(substr($url, -1)!='/' && substr($method, 0, 1)!='/')$url.='/';
 $url.=$method;
 $postfields=http_build_query($params);
 if($format!='xml')$format='json';
 if($request!='post' && $request!='put' && $request! ='delete')$request='get';
 $ci=curl_init();
 curl_setopt($ci, CURLOPT_SSL_VERIFYPEER, FALSE);
 curl_setopt($ci, CURLOPT_RETURNTRANSFER, 1);
 curl_setopt($ci, CURLOPT_CONNECTTIMEOUT, 30);
 curl_setopt($ci, CURLOPT_TIMEOUT, 30);
 switch($request){
 case 'get':
 $url.='?'.$postfields;
 break;
 case 'post':
 curl_setopt ($ci, CURLOPT_POST, TRUE);
 curl_setopt($ci, CURLOPT_POSTFIELDS, $postfields);
 break;
 case 'put':
 curl_setopt($ci, CURLOPT_CUSTOMREQUEST, 'PUT');
 curl_setopt($ci, CURLOPT_POSTFIELDS , $postfields);
 $headers[]='X-HTTP-Method-Override: PUT';
 break;
 case 'delete': //Not tested
 curl_setopt($ci, CURLOPT_CUSTOMREQUEST, 'DELETE');
 curl_setopt($ci, CURLOPT_POSTFIELDS, $postfields);
 break;
 }
 $headers[]='User-Agent: mini_rest_client(piscdong.com)';
 $headers[]='Accept: application/'.$format ;
 curl_setopt($ci, CURLOPT_HTTPHEADER, $headers);
 curl_setopt($ci, CURLOPT_URL, $url);
 $response=curl_exec($ci);
 curl_close($ci);
 if($response!=' '){
 if($format=='json'){
 return json_decode($response, true);
 }else{
 return simplexml_load_string($response);
 }
 }
}

function array2xml($array){
 $xml='';
 foreach($array as $k=>$v){
 $xml.='<'.$k .'>';
 if(is_array($v)){
 $xml.=array2xml($v);
 }else{
 $xml.=$v;
 }
 $xml.='';
 }
 return $xml;
}

$format='json';
if(isset($_SERVER['HTTP_ACCEPT']) && $_SERVER['HTTP_ACCEPT']= ='application/xml')$format='xml';
$return['format']=$format;

$method='';
if(isset($_SERVER['PATH_INFO']) && $_SERVER ['PATH_INFO']!=''){
 if(substr($_SERVER['PATH_INFO'], 0, 1)=='/')$method=substr($_SERVER['PATH_INFO'], 1);
}
if($method!=''){
 $return['method']=$method;
}else{
 $return['method_err']='no method';
}

$request= '';
if(isset($_SERVER['REQUEST_METHOD']) && $_SERVER['REQUEST_METHOD']!=''){
 switch($_SERVER['REQUEST_METHOD']){
 case 'GET':
 $ request='get';
 foreach($_GET as $k=>$v)$return['param_'.$k]=$v;
 break;
 case 'POST':
 $request='post' ;
 foreach($_POST as $k=>$v)$return['param_'.$k]=$v;
 break;
 case 'PUT':
 $request='put';
 $param= file_get_contents("php://input");
 if($param!=''){
 parse_str($param, $param_r);
 foreach($param_r as $k=>$v)$return[' param_'.$k]=$v;
 }
 break;
 case 'DELETE':
 $request='delete';
 $param=file_get_contents("php://input");
 if($param! =''){
 parse_str($param, $param_r);
 foreach($param_r as $k=>$v)$return['param_'.$k]=$v;
 }
 break;
 }
}
if($request!=''){
 $return['request']=$request;
}else{
 $return['request_err']='no request';
}

if($ format=='json'){
 echo json_encode($return);
}else{
 echo '';
 echo array2xml($return);
 echo '';
}