Marker coordinates not correct leaflet

I am creating a Admin/User Control Panel of a game called ArmA 3 using a mod called Exile. Exile places X,Y (Z aswell) coordinates in a database. I am using PHP to grab those coordinates and place a marker where the player is located using leaflet.js. I am using a custom image (15360x15360).

Problem: Lets say that I'm at position (6340, 7801) (x,y). The marker will be off from where I'm actually located (see imgurs below)

(ingame location) https://imgur.com/a/Nky9Oqf

(leaflet marker) https://imgur.com/a/jFco4V5

PHP code + leaflet.js:

<?php
require_once "application.php";
?>
<html lang="en">
    <head>
        <title>Search</title>
        <link rel="stylesheet" href="leaflet.css">
        <meta charset="UTF-8">
    </head>
    <body>

<?php

if(isset($_GET["q"])) {
    $uid = $_GET["q"];

    $UCP = new UCP("localhost", "root", "root", "testdb", "3306");
    $r = $UCP->getPlayer($uid);
    if($r) {
        $coords = $UCP->getPlayerCoords($uid);
    }
}

?>

<div id="map" style="height: 100%"></div>

<script src="js/leaflet.js"></script>
<script>

var mapMinZoom = 0;
var mapMaxZoom = 4;
var map = L.map('map', {
    minZoom: mapMinZoom,
    maxZoom: mapMaxZoom,
    center: [15360, 15360],
    crs: L.CRS.Simple
});

var w = 15360,
    h = 15360,
    url = 'http://localhost/images/Chernarus_Isles_nogrid.png';

var southWest = map.unproject([0, h], mapMaxZoom);
var northEast = map.unproject([w, 0], mapMaxZoom);
var bounds = new L.LatLngBounds(southWest, northEast);

map.fitBounds(bounds);

L.imageOverlay(url, bounds).addTo(map);

<?php

    if(isset($_GET["q"])) {
        if($r) { ?>
            var pos_x_player = Math.round(<?php echo $coords["pos_x"]; ?>);
            var pos_y_player = Math.round(<?php echo $coords["pos_y"]; ?>);
            var p_loc = map.unproject([pos_y_player, pos_x_player], mapMaxZoom);
            L.marker(p_loc).addTo(map).bindPopup('Player Location');
            <?php

        }
    }

?>
</script>

It successfully connects to the database and grabs the coordinates but leaflet is always off from where I am actually located.

Any help would be appreciated. If I missed anything please let me know :)