request.responseText接收正确的数据，但JavaScript无法理解

I am new to AJAX and presently learning it from Head First AJAX. The problem I am facing is really weird. I developed a simple program that creates a request through JavaScript and then shows the output.

main.js

window.onload = initPage;
function initPage() {
    request = createRequest();
    if(request == null) {
        alert("request could not be created");
    }
    else {
        var url = "requestMe.php";
        request.onreadystatechange = showResult;
        request.open("GET", url, true);
        request.send(null);
    }
 }

function showResult() {
    if(request.readyState == 4) {
        if(request.status == 200) {
            if(request.responseText == "okay") {
                alert("A successful request was returned");
            }
            else {
                alert("ALERT : " + request.responseText);
            }
         }
         else {
            alert("Request status received was not correct");
         }
    }
}

//--function to create request objects--
function createRequest(){
   try{
       request = new XMLHttpRequest();
   }
   catch(tryMS){
       try{
           request = new ActiveXObject("Msxm12.XMLHTTP");
       }
       catch(otherMS){
           try{
               request = new ActiveXObject("Microsoft.XMLHTTP");
           }
           catch(failed){
               request = null;
           }
       }
    }
    return request;
}

Now, here is the php script.

requestMe.php

<?php
   echo 'okay';
?>

This code should give the alert A successful request was returned

But instead it gives the result ALERT : okay

The weird thing is this same code was working yesterday for me when I tried it and now it is giving me this result. I tried to create similar programs and they all are showing me this kind of weird behavior. The responseText received is correct because it appends okay after ALERT :. What wrong am I doing here in the code? Why is it going to the else part when the responseText received is correct?

Any Help? Thanks in advance.

Do one thing add exit; after echo 'okay';

Issue in your code is after ?> there is extra space available you can fix it either by removing ?> or removing extra space after ?>.

I hope it will fix your issue.

I personally would do it using jQuery's Ajax Function in the following way:

document.addEventListener("DOMContentLoaded", function()
{
  $.ajax({
    "url": "requestMe.php"  
  }).done(function(data)
  {
    if(data == "okay")
    {
      alert("A successful request was returned");
    } else
    {
      alert("ALERT : " + data);
    }
  }).fail(function()
  {
     alert("Connection Failed");
  });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

I haven't tested this Script, but it should in theory work out well.

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