在下面的评论中，您告知我们您正在使用$_FILES语法来检索文件。这意味着您要创建一个multipart/form-data请求。该过程基本上是：

1. 为您的multipart/form-data请求指定边界。

2. 指定Content-Type请求的一个，以指定该请求multipart/form-data及其边界。

3. 创建请求正文，将各个组成部分分开（每个发布的值以及每个上传之间的值）。

有关更多详细信息，请参见RFC 7578。无论如何，在Swift
3和更高版本中，这可能看起来像：

/// Create request
///
/// - parameter userid:   The userid to be passed to web service
/// - parameter password: The password to be passed to web service
/// - parameter email:    The email address to be passed to web service
///
/// - returns:            The `URLRequest` that was created

func createRequest(userid: String, password: String, email: String) throws -> URLRequest {
    let parameters = [
        "user_id"  : userid,
        "email"    : email,
        "password" : password]  // build your dictionary however appropriate

    let boundary = generateBoundaryString()

    let url = URL(string: "https://example.com/imageupload.php")!
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.setValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")

    let fileURL = Bundle.main.url(forResource: "image1", withExtension: "png")!
    request.httpBody = try createBody(with: parameters, filePathKey: "file", urls: [fileURL], boundary: boundary)

    return request
}

/// Create body of the `multipart/form-data` request
///
/// - parameter parameters:   The optional dictionary containing keys and values to be passed to web service.
/// - parameter filePathKey:  The optional field name to be used when uploading files. If you supply paths, you must supply filePathKey, too.
/// - parameter urls:         The optional array of file URLs of the files to be uploaded.
/// - parameter boundary:     The `multipart/form-data` boundary.
///
/// - returns:                The `Data` of the body of the request.

private func createBody(with parameters: [String: String]?, filePathKey: String, urls: [URL], boundary: String) throws -> Data {
    var body = Data()

    parameters?.forEach { (key, value) in
        body.append("--\(boundary)\r\n")
        body.append("Content-Disposition: form-data; name=\"\(key)\"\r\n\r\n")
        body.append("\(value)\r\n")
    }

    for url in urls {
        let filename = url.lastPathComponent
        let data = try Data(contentsOf: url)
        let mimetype = mimeType(for: filename)

        body.append("--\(boundary)\r\n")
        body.append("Content-Disposition: form-data; name=\"\(filePathKey)\"; filename=\"\(filename)\"\r\n")
        body.append("Content-Type: \(mimetype)\r\n\r\n")
        body.append(data)
        body.append("\r\n")
    }

    body.append("--\(boundary)--\r\n")
    return body
}

/// Create boundary string for multipart/form-data request
///
/// - returns:            The boundary string that consists of "Boundary-" followed by a UUID string.

private func generateBoundaryString() -> String {
    return "Boundary-\(UUID().uuidString)"
}

/// Determine mime type on the basis of extension of a file.
///
/// This requires `import MobileCoreServices`.
///
/// - parameter path:         The path of the file for which we are going to determine the mime type.
///
/// - returns:                Returns the mime type if successful. Returns `application/octet-stream` if unable to determine mime type.

private func mimeType(for path: String) -> String {
    let pathExtension = URL(fileURLWithPath: path).pathExtension as NSString

    guard
        let uti = UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension, pathExtension, nil)?.takeRetainedValue(),
        let mimetype = UTTypeCopyPreferredTagWithClass(uti, kUTTagClassMIMEType)?.takeRetainedValue()
    else {
        return "application/octet-stream"
    }

    return mimetype as String
}

带有：

extension Data {

    /// Append string to Data
    ///
    /// Rather than littering my code with calls to `data(using: .utf8)` to convert `String` values to `Data`, this wraps it in a nice convenient little extension to Data. This defaults to converting using UTF-8.
    ///
    /// - parameter string:       The string to be added to the `Data`.

    mutating func append(_ string: String, using encoding: String.Encoding = .utf8) {
        if let data = string.data(using: encoding) {
            append(data)
        }
    }
}

拥有所有这些后，您现在需要提交此请求。我建议这是异步完成的。例如，使用URLSession，您将执行以下操作：

let request: URLRequest

do {
    request = try createRequest(userid: userid, password: password, email: email)
} catch {
    print(error)
    return
}

let task = URLSession.shared.dataTask(with: request) { data, response, error in
    guard let data = data, error == nil else {
        // handle error here
        print(error ?? "Unknown error")
        return
    }

    // parse `data` here, then parse it

    // note, if you want to update the UI, make sure to dispatch that to the main queue, e.g.:
    //
    // DispatchQueue.main.async {
    //     // update your UI and model objects here
    // }
}
task.resume()