Google Script Error on Post - php

Question

I am posting data to google sheets using php, everytime I post the data it get added on the sheet correctly, but i get the error message as
We8d#39;re sorry, a server error occurred. Please wait a bit and try
again.
My php curl post code is:
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $gsurl);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
$output = curl_exec($ch);
$info = curl_getinfo($ch);
curl_close($ch);
$res = json_decode($output, 1);
My GS App Script is :
var SCRIPT_PROP = PropertiesService.getScriptProperties(); // new property service
function doGet(e){
return handleResponse(e);
}
function doPost(e){
return handleResponse(e);
}
function handleResponse(e) {
var lock = LockService.getPublicLock();
lock.waitLock(30000);
try {
var doc = SpreadsheetApp.openById(SCRIPT_PROP.getProperty("key"));
var sheet = doc.getSheetByName(SHEET_NAME);
var headRow = e.parameter.header_row || 1;
var headers = sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues()[0];
var nextRow = sheet.getLastRow()+1;
var row = [];
for (i in headers){
if (headers[i] == "Timestamp"){
row.push(new Date());
} else {
row.push(e.parameter[headers[i]]);
}
}
sheet.getRange(nextRow, 1, 1, row.length).setValues([row]);
// return json success results
return ContentService
.createTextOutput(JSON.stringify({"result":"success", "row": nextRow}))
.setMimeType(ContentService.MimeType.JSON);
} catch(e){
return ContentService
.createTextOutput(JSON.stringify({"result":"error", "error": e}))
.setMimeType(ContentService.MimeType.JSON);
} finally {
lock.releaseLock();
}
}
function setup() {
var doc = SpreadsheetApp.getActiveSpreadsheet();
SCRIPT_PROP.setProperty("key", doc.getId());
}
Please help me.