我的代码无法在线运行

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                    <p class="mb0 mt6">Closed <span title="2014-07-22 08:33:38Z" class="relativetime">5 years ago</span>.</p>
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<?php
include('changeLang.php'); 
$default_language = 'sr';
if(isset($_COOKIE['lang'])) {
    $lang = $_COOKIE['lang'];
} 
else {
    $lang = $default_language;
} 
if($lang == 'en') { 
    include('language_en.php');
} 
else {
    include('language_sr.php');
}
?>

I added a new URL path and I do not eject any error, Of course it's all in the same folder and there is no subfolders to immediately exclude the possibility. I think about mistake

<script  type="text/javascript">
function changeLanguage (lang) {

    $.ajax({
        url: 'http://www.example.com/changeLang.php',
        type: 'POST',
        data:{ lang:lang },
        beforeSend: function(){

        },
        complete: function(){

        },
        success: function(data) {             
            console.log(data);
            if(data == 'ok'){
                location.reload();
            }
            //var response = JSON.parse(data);
        },
        error: function(data, textStatus, errorThrown){
            console.log("error"+' '+JSON.stringify(data) + textStatus  + errorThrown);
        }
    });
}
</script>

// in code

My mistke was in href, because i put href="" , the page was reloading at first and onclick functions never been used, so i have to put javascript:void(0) and in css curosr:pointer for div #flag....

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You are requesting changeLang.php, which won't be the name of the file online. You'll need the full URL. The same applies to the image files.

For example, in the ajax section of the script, you have

$.ajax({
    url: 'changeLang.php',

Instead of requesting changeLang.php, add in the full file name, like http://www.example.com/site/changeLang.php. This specifies which server you're expecting to serve the file, and where you know it to be.

Locally, there is almost always only one server, and often a much simpler directory structure, cutting down on these mistakes. As soon as you put it online, the mistakes show up as errors. Remember also that error reporting settings for a live site will typically be much harsher than those in a development environment. You might want to check out your php.ini file, both locally and online. You can tune it temporarily to show you all the fine details. It might help you figure out the problem.