上传文件到web服务器(iphone)

下面的代码可以上传文件，
NSData *imageData = UIImageJPEGRepresentation(image.image, 90);
    // setting up the URL to post to
    NSString *urlString = @"http://localhost/test-upload.php";

    
    // setting up the request object now
    NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease];
    [request setURL:[NSURL URLWithString:urlString]];
    [request setHTTPMethod:@"POST"];
    
    /*
     add some header info now
     we always need a boundary when we post a file
     also we need to set the content type
    
     You might want to generate a random boundary.. this is just the same
     as my output from wireshark on a valid html post
    */
    NSString *boundary = [NSString stringWithString:@"---------------------------14737809831466499882746641449"];
    NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];
    [request addValue:contentType forHTTPHeaderField: @"Content-Type"];
    
    /*
     now lets create the body of the post
    */
    NSMutableData *body = [NSMutableData data];
    [body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];    
    [body appendData:[[NSString stringWithString:@"Content-Disposition: form-data; name=\"userfile\"; filename=\"ipodfile.jpg\"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
    [body appendData:[NSData dataWithData:imageData]];

    
    [body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
    
    NSString *udid = @"data=0000000000000000000000000000000000000002"; // 添加一个data字段，但是后台接收不到。
    [body appendData:[udid dataUsingEncoding: NSUTF8StringEncoding allowLossyConversion:YES]];  
        


    
    // setting the body of the post to the reqeust
    [request setHTTPBody:body];
    

// web 服务器端
<?php
$fp=fopen("t.txt","w");
fwrite ( $fp, $_POST["data"]  ); // 取不到值，不知道为何，请指点。
fclose($fp);
move_uploaded_file($_FILES['userfile']['tmp_name'], "t.jpg");