Ajax验证码检查

So basically I have this ajax code in my index.php that works:

 $(function() {
  $("#submitbtn").click(function() {
    var txt_from = $("#txt_from").val();
    var txt_body = $("#txt_body").val();
    var captcha_code = $("#captcha_code").val();
    var txt_number = $("#txt_number").val();
    var dataString = 'txt_from=' + txt_from + '&txt_body=' + txt_body + '&captcha_code=' + captcha_code + '&txt_number=' + txt_number;
    if (txt_body == '' || txt_number == '' || txt_from == '' || captcha_code == '') {
      $('.alertsuccess').fadeOut(200).hide();
      $('.alerterror').fadeIn(200).show();
      //$('.alert-box').fadeIn(200).show();
    } else {
      $.ajax({
        type: "POST",
        url: "sendsms.php",
        data: dataString,
        success: function() {
          $('.alertsuccess').fadeOut(200).hide();
          $('.alertsuccess').fadeIn(200).show();
          $('.alerterror').fadeOut(200).hide();
          document.getElementById('captcha').src = 'securimage/securimage_show.php?' + Math.random();
          $('#txt_from').val('');
          $('#txt_body').val('');
          $('#txt_number').val('');
          $('#captcha_code').val('');
        }
      });
    }
    return false;
  });
});

And in my sendsms.php

 <?php
session_start();

if ($_POST) {
  include_once 'securimage/securimage.php';

  // header('Location: maintenance.php');

  $securimage = new Securimage();
  include "smsGateway.php";

  include "filter.php";

  $smsGateway = new SmsGateway('email@gmail.com', 'pword');
  if ($securimage->check($_POST['captcha_code']) == false) {
    echo "<script>alert('The security code entered was incorrect. Please go back and try again.');window.location.href='javascript:history.go(-1)';</script>";
    exit;
  }

  $numto = sanitize($_POST['txt_number']);
  $num = "+63" . $numto;
  $deviceID = 1254;
  $number = $num;
  $from = $_POST['txt_from'];
  $message = $from . ":
" . sanitize($_POST['txt_body']);
  $result = $smsGateway->sendMessageToNumber($number, $message, $deviceID)
}

?>

The captcha code also works but the problem is I want to show error in my index.php if captcha is wrong instead of alerting it on sendsms.php. Is it possible? Thank you

in your HTML form imbed the page URL or page name in a hidden input

 <input type="hidden" name="back" value="index.html" />

PHP

<?php
session_start();
if (file_exists($_POST['back']) {
  include_once 'securimage/securimage.php';
  $securimage = new Securimage();
  if ($securimage->check($_POST['captcha_code']) == false) {
    include($_POST['back']);
    exit;
  }
  include "smsGateway.php";
  include "filter.php";
  $smsGateway = new SmsGateway('email@gmail.com', 'pword');

You can do it by creating a json encoded response on your php file.

echo json_encode(array( 'status' => 'failed', 'message'=> 'The security code entered was incorrect. Please go back and try again.' ));

Then on your ajax success, check if it returned a success status.

Your script

$(function() {
  $("#submitbtn").click(function() {
    var txt_from = $("#txt_from").val();
    var txt_body = $("#txt_body").val();
    var captcha_code = $("#captcha_code").val();
    var txt_number = $("#txt_number").val();
    var dataString = 'txt_from=' + txt_from + '&txt_body=' + txt_body + '&captcha_code=' + captcha_code + '&txt_number=' + txt_number;
    if (txt_body == '' || txt_number == '' || txt_from == '' || captcha_code == '') {
      $('.alertsuccess').fadeOut(200).hide();
      $('.alerterror').fadeIn(200).show();
      //$('.alert-box').fadeIn(200).show();
    } else {
      $.ajax({
        type: "POST",
        url: "sendsms.php",
        data: dataString,
        success: function(response) {
          response = $.parseJSON(response);
          if (response) {
            if (response.status == 'success') {
              $('.alertsuccess').fadeOut(200).hide();
              $('.alertsuccess').fadeIn(200).show();
              $('.alerterror').fadeOut(200).hide();
              document.getElementById('captcha').src = 'securimage/securimage_show.php?' + Math.random();
              $('#txt_from').val('');
              $('#txt_body').val('');
              $('#txt_number').val('');
              $('#captcha_code').val('');
            } else if (response.status == 'failed') {
              $("#divToErrorMessage").html(response.message);
            }
          }
        }
      });
    }
    return false;
  });
});

PHP

<?php
session_start();

if ($_POST) {
  include_once 'securimage/securimage.php';

  // header('Location: maintenance.php');

  $securimage = new Securimage();
  include "smsGateway.php";

  include "filter.php";

  $smsGateway = new SmsGateway('email@gmail.com', 'pword');
  if ($securimage->check($_POST['captcha_code']) == false) {
    echo json_encode(array( 'status' => 'failed', 'message'=> 'The security code entered was incorrect. Please go back and try again.' )); 
  }
  else {
    $numto = sanitize($_POST['txt_number']);
    $num = "+63" . $numto;
    $deviceID = 7621;
    $number = $num;
    $from = $_POST['txt_from'];
    $message = $from . ":
" . sanitize($_POST['txt_body']);
    $result = $smsGateway->sendMessageToNumber($number, $message, $deviceID);
    echo json_encode(array( 'status' => 'success', 'message'=> 'The security code entered was correct.' )); 
  }
}

?>