DIV container stays blank - php

Question

I need to run the function find_optimal_schedule() every 5 seconds, while each time updating the DIV container schedule. Below is my code snippet. The problem is that alert("Init") is executed, while alert("True") or alert("False") are not executed. FireBug shows that optimize.php is runned every 5 seconds, but I don't understand why the content of DIV container stays blank all the time.
P.S. The code gantt.php works properly, because I tested it in DIV container without the timer and the Gantt chart was displayed correctly. Therefore, I do not provide this code here, because it's not the case.
scheduler.php
<script>
window.setInterval(function(){
find_optimal_schedule();
}, 5000);
</script>
<script>
function find_optimal_schedule() {
$.ajax({
url: 'modules/mod_scheduler/pages.php?page=optimize.php',
dataType: 'json',
success: function(output){
alert("Init");
if(output.msg === 1){
alert("True");
$('#schedule').html(output.html);
} else {
alert("False");
return false;
}
}
});
}
</script>
<div style="width:100%; height:350px; position:relative" id="schedule" class="schedule"></div>
pages.php
<?php
#session_start();
#$pag_mod = $_GET['pag_mod'];
if(!isset($pag_mod))
$pag_mod = 0;
if (isset($_GET['pag_mod'])) {
include 'modules/mod_scheduler/'.$_GET['pag_mod'];
}
else {
include 'modules/mod_scheduler/scheduler.php';
}
?>
optimize.php
<?php
// Dispay Gantt chart
$html_code = '<img src="modules/mod_scheduler/gantt.php">';
echo json_encode(array('msg' => 1, 'html' => $html_code));
?>

Answer 1

I believe you output.msg should be compared with == instead of ===.
if(output.msg == 1){
alert("True");
$('#schedule').html(output.html);
} else {
alert("False");
return false;
}
Via nnnnn, it appears that === is valid for comparision in javascript; therefore, the only thing I can think of is that output.msg is undefined. Since === is not causing the javascript error, output.msg is the only other thing that could be.

Answer 2

You are using a strict equality operator (===) instead of equality.
This means that the comparison is true if also the data types are considered equal, in addition to the values; maybe output.msg comes as a string and is not equated to a number. Try == instead.

Answer 3

Try
console.log(output)
to see if output is a valid object. Firebug should show you the entire object with all its properies.