PHP创建的图像文件json_encode返回SyntaxError：JSON.parse：数据意外结束

Question

First time poster, be gentle. Anyway I'll try and make this as clear as possible.

I have a site that uses a combination of jQuery/Ajax and PHP to create offer 'coupons'. When a user visits, they select the coupons they want to buy (via PayPal) and submit. I'm sending this to paypal and listening for the IPN within my PHP script and in the case of a Valid IPN the script should proceed to assign a randomly generated 12 digit 'barcode' to the coupons they chose, add them all to a file that is opened for printing. I'm storing the selected coupon data (name array) using this jQuery plugin

The initial coupon generation works, the paypal integration (including the IPN listener) works. I can see the cookies in the console while I'm testing this so my form data is there. I'm even getting the 'success' portion of the json array.

My issues is that I'm trying to fetch the image file via ajax but I am getting 'SyntaxError: JSON.parse: unexpected end of data' and I can't figure out why. The image creation code was already written prior to me taking this on, I just needed to tie it together with paypal.

my-offers.php

$(window).load(function(){

  var extradata = {};
  extradata.action = 'createCoupon';
  extradata.offers = $.cookies.get("offers");
  console.log(extradata);
    $.ajax({
      url: 'api/data_request.php',
      success: function(e, data, result){
          console.log('done!', data);   
              //this returns 'success' but console.log('done!', e) returns empty string

        //below is throwing unexpected end of data
        var resultObj = JSON.parse(e);
                        if(resultObj.result === 'success'){
                            //console.log('success!'+resultObj);
                            window.open(resultsObj.filename, '_blank');
                        }else{
                            console.log('some sort of error!', data);
                        }
                    },
                    type: 'POST',
                    data: extradata,
                    error: function(e, data, extra){
                            console.log('there was a serious error!', e, data, extra);
                            console.log(data.errorThrown, data.textStatus, data.jqXHR);
                    }                       
                });

data-request.php

//go through finished coupons array, and put them all on one image
            //then save the image in coupons
            $finalimg = imagecreatetruecolor($thewidth, $theheight);
            $cursor = 0;
            for($i = 0; $i<4; $i++){
                $obj = $finishedCoupons[$i];
                $coupon = $obj[0];
                $width = $obj[1];
                $height = $obj[2];
                $copyied = imagecopymerge($finalimg, $coupon, 0, $cursor, 0, 0, $width, $height, 100); 
                if($copyied === false){
                    returnError('error copying images');
                }
                $cursor = $cursor+$height;
            }
            $didit = imagejpeg($finalimg, '/images/coupons/'.$thefilename.'.jpg', 100);
            if($didit === false){
                returnError('final copying error'.$thefilename);
            }else{


                echo json_encode(array('result'=>'success', 'filename'=>'images/coupons/'.$thefilename.'.jpg'));
                die();

            }

MySQL select the coupons and create barcodes (for context)

//get the coupon picture we'll put the numbers on
                    $success1 = $mysqli->prepare("SELECT title, text, realcoupon FROM offers WHERE offer_id = ? LIMIT 1");
                    $success1->bind_param('i', $coupon);
                    $success1->execute();
                    $success1->store_result();
                    $success1->bind_result($title, $text, $source);
                    $success1->fetch();                 
                //now actually generate the numbers
                //perform database collision detection
                //number is 12 digits long so we can use it in a barcode if needed
                    $exists = 1;
                       while($exists !== 0){ 
                        $code = generateRandomNumber();
                        $success1 = $mysqli->prepare("SELECT barcode FROM offerId WHERE barcode = ?");
                        $success1->bind_param('s', $code);
                        $success1->execute();
                        $success1->store_result();
                        $exists = $success1->num_rows;
                       }
                    $thefilename.=$code;
                //$code is a unique barcode now, so we should insert it into the array
                // coupon contains the offer_id
                $success = $mysqli->prepare("INSERT INTO offerId (offer_id, barcode, date) VALUES (?, ?, CURRENT_TIMESTAMP)");
                $success->bind_param('is', $coupon, $code);
                $success->execute();
                //$success->store_result();
                //$success->fetch();
                $affected = $success->affected_rows;
                if($affected !== 1){
                    returnError($affected);
                    returnError('Error inserting the barcode!');
                }                   
                //now put the numbers on the coupon and push it to the finishedCoupons array
                $source = '../images/'.$source;
                try{
                   $extension = pathinfo($source, PATHINFO_EXTENSION);
                   if(!file_exists($source)){
                    returnError('Cant find coupon!');
                    return false;
                   }
                   $info = getimagesize($source);
                   if($info === false){
                      returnError("InvalidImage");
                      return false;
                   }
                }catch (Exception $e){
                    returnError("InvalidImage");
                    return false;
                }
                $type    = $info[2];
                $width   = $info[0]; // you don't need to use the imagesx and imagesy functions
                $height  = $info[1];
                if($width>$thewidth){
                    $thewidth = $width;
                }

I've tried setting the php file to header('Content-type: application/json'); I've tried calling dataType: 'json' in my ajax call. I've even run php -l data_request.php to check for syntax errors and nothing was returend. Nothing seems to work. This is the last step I need to debug!! I've been working on this for hours.

After inspecting the response header, it looks like it's being transferred as type text/html instead of text/json or application/json

Answer 1

The last line of your PHP is the problem:

echo json_encode(array('result'=>'success', 
                       'filename'=>'images/coupons/'.$thefilename.'.jpg'));
die(); echo $coupons;

When you write PHP services, you should only be echo'ing the JSON nothing else, or the JSON response data won't be valid since it is being concatenated with another string.

You must echo JSON ONLY :

echo json_encode(array('result'=>'success', 
                       'filename'=>'images/coupons/'.$thefilename.'.jpg'));
die(); //echo $coupons;

Answer 2

Found the issue.

IPN is not real time, and since the client here needed to interrupt the payment flow here in the case that the payment (ipn) failed, this didn't work, which in turn caused the JSON to be partially empty since it was wrapped in an if() with the paypal IPN. So I changed this out with paypal PDT (payment data transfer) which is instant, and then verified against the transaction id and payment amount.