How to handle PHP errors in Swift

There are two questions. One is PHP and the other is Swift.

• Your PHP should never really just report an error. I would assume it always returns JSON. This will make it easier for your client code to detect and handle errors appropriately.

  <?php
  
  header("Content-Type: application/json");
  
  $response = array();
  
  error_reporting(0);
  ini_set('error_reporting', E_ALL);
  ini_set('display_errors','Off');
  if (!isset($_REQUEST['password'])) {
      $response["success"] = false;
      $response["error_code"] = 1;
      $response["error_message"] = "No password provided";
      echo json_encode($response);
      exit();
  } 
  
  $mysqli = new mysqli("localhost", "root", $_REQUEST['password'], "");
  if ($mysqli->connect_errno) {
      $response["success"] = false;
      $response["error_code"] = 2;
      $response["mysql_error_code"] = $mysqli->connect_errno;
      $response["error_message"] = $mysqli->connect_error;
      echo json_encode($response);
      exit();
  }
  
  if ($res = $mysqli->query("SHOW DATABASES")) {
      $dbs = array();
      $res->data_seek(0);
      if ($res->num_rows > 0) {
          while($row = $res->fetch_assoc()) {
              $dbs[] = $row;
          }
          $response["success"] = true;
          $response["results"] = $dbs;
      } else {
          $response["success"] = false;
          $response["error_code"] = 3;
          $response["error_message"] = "Failed to get list of databases from server.";
      }
  
      $res->close();
  } else {
      $response["success"] = false;
      $response["error_code"] = 4;
      $response["mysql_error_code"] = $mysqli->errno;
      $response["error_message"] = $mysqli->error;
  }
  $mysqli->close();
  
  echo json_encode($response);
  
  ?>
  
        
  
          
          
          
        
  
      

  Note:

  • Sets the title application/json
    
    for Content-Type
    
    ;

  • Always returns a dictionary containing

    • the key "success", which is either true or false;

    • if error, a error_code
      
      indicating the type of error (1 = no password specified; 2 = connection failed, 3 = no databases found, 4 = some SQL error);

    • if error, a string error_msg
      
      indicating the error message string; and

    • if success, an array results
      
      (just like you used to return at the root level).

• On the Swift side, you need:

  • Modify it to look for these various server-level errors (note that I am making the top-level structure a dictionary, and your original array of dictionaries a specific value;

  • You might want to proactively check the statusCode
    
    object response
    
    to make sure the server provided a return code 200
    
    (for example, 404
    
    means the page was not found, etc.) ..);

  • You can also check for JSON errors for parsing (in case some error on the server did not allow to return correct JSON); and

  • You should really avoid the password (because if it includes +
    
    or characters &
    
    , it won't pass successfully otherwise).

  Thus, you might have something like:

  let encodedPassword = password.stringByAddingPercentEncodingForURLQueryValue()!
  let body = "password=\(encodedPassword)"
  let request = NSMutableURLRequest(URL: URL!)
  request.HTTPBody = body.dataUsingEncoding(NSUTF8StringEncoding)!
  request.HTTPMethod = "POST"
  
  let task = NSURLSession.sharedSession().dataTaskWithRequest(request) { data, response, error in
  
      // detect fundamental network error
  
      guard error == nil && data != nil else {
          print("network error: \(error)")
          return
      }
  
      // detect fundamental server errors
  
      if let httpResponse = response as? NSHTTPURLResponse where httpResponse.statusCode != 200 {
          // some server error
          print("status code was \(httpResponse.statusCode); not 200")
          return
      }
  
      // detect parsing errors
  
      guard let responseObject = try? NSJSONSerialization.JSONObjectWithData(data!, options: []) as? [String : AnyObject] else {
          // some problem parsing the JSON response
          print(String(data: data!, encoding: NSUTF8StringEncoding))
          return
      }
  
      // now parse app-level response to make sure `status` was `true`
  
      guard let success = responseObject!["success"] as? NSNumber else {
          print("Problem extracting the `success` value") // we should never get here
          return
      }
  
      if !success.boolValue {
          print("server reported error")
          if let errorCode = responseObject!["error_code"] as? NSNumber {
              switch (errorCode.integerValue) {
              case 1:
                  print("No password provided")
              case 2:
                  print("Connection failed; probably bad password")
              case 3:
                  print("No databases found")
              case 4:
                  print("Some SQL error")
              default:
                  print("Unknown error code: \(errorCode)") // should never get here
              }
          }
          if let errorMessage = responseObject!["error_message"] as? String {
              print("  message=\(errorMessage)")
          }
          return
      }
  
      if let databases = responseObject!["results"] as? [[String : AnyObject]] {
          print("databases = \(databases)")
      }
  }
  task.resume()
  
        
  
          
          
          
        
  
      

  Percentage skipping code is in the category String
  
  :

  extension String {
  
      // see RFC 3986
  
      func stringByAddingPercentEncodingForURLQueryValue() -> String? {
          let characterSet = NSCharacterSet(charactersInString:"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-._~")
          return self.stringByAddingPercentEncodingWithAllowedCharacters(characterSet)
      }
  }
  
        
  
          
          
          
        
  
      

Several other auxiliary observations:

• Never send passwords to the box. Put them in the request body POST
  
  (not the URL) and then use the URL https
  
  .

• I personally would not use the MySQL password part for application level authentication. I would keep the MySQL authentication logic server side coded and then use your own user authentication table.