Error the language is not changed when I am in a url with different folders or directories

Question

The following parameter adds a language to my website:

if(isset($_COOKIE['language'])){
    if($_COOKIE['language']==='en'){
        $WEBSITE_TITLE = " | SITE EN";
        $LANG = 'en';
        $language = "en";
    }elseif($_COOKIE['language']==='es'){
        $WEBSITE_TITLE = " | SITE ES";
        $LANG = 'es';
        $language = "es";
    }
} else {
    $WEBSITE_TITLE = " | SITE EN";
    $LANG = 'en';
    $language = "en";
}

And through Ajax I can change the language of my website either in Spanish or English:

$(function() {
    $(".lang").click(function(e) {
        e.preventDefault();
        var language = $(this).attr('data-lang');
        var postData={lang: language};

        var request = $.ajax({
            method : 'POST',
            url    : 'language.ini.php',
            data   : postData,
            dataType: "html"
        });
        request.done(function(data) {
            //$("html").html(data);
            //location.reload();
            //location.href = '/index.php';
            setTimeout(function(){
                location.reload();
            },100);
        });
        request.fail(function(jqXHR, textStatus) {
            alert("Error!: " + textStatus);
        });
    });
});

The data sent by Ajax is received through the following parameters:

if (isset($_POST['lang'])) {
    $lang = $_POST['lang'] ?: '';

    if ($lang === "en") {
        setcookie ('language', 'en', time()+60*60*24*365, '/', 'example.com');
    } elseif ($lang === "es") {
        setcookie ('language', 'es', time()+60*60*24*365, '/', 'example.com');
    }
}

But the error is when I try to change the language in a url with several folders or directories:

example.com/es/folders2/folders3/folders4/url-of-article/

Currently the code to change the language only works for me on these pages:

example.com
example.com/index.php

Answer 1

Change dataType: "html" to dataType: "json" and add console.error(jqXHR); in to your fail function goto console see what you get.

You probably having problem with data type.

I tested this and it works fine for me :

 $(function() {
    $(".lang").click(function(e) {
        e.preventDefault();
        var language = $(this).attr('data-lang');
        var postData={lang: language};

        var request = $.ajax({
            method : 'POST',
            url    : 'language.ini.php',
            data   : language,
            dataType: "JSON"
        });
        request.done(function(data) {
            //$("html").html(data);
            //location.reload();
            //location.href = '/index.php';
            $("#results").html(data); //show data
            setTimeout(function(){
                location.reload();
            },100);
        });
        request.fail(function(jqXHR, textStatus) {
                        console.error(jqXHR);
            alert("Error!: " + textStatus);
        });
    });
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="lang"> click me </div>
<div id="result"> </div> // Conent will show in this div.