visitor counters

<?php
// Only allow the script to be run from nuel.pw
header('Access-Control-Allow-Origin: https://nuel.pw');
// Get the current value
$fn = 'count.txt';
$current = intval(file_get_contents($fn));
// Only increment once per browsing session
session_start();
if ($_SESSION['count-nuel'] !== 1) {
    $_SESSION['count-nuel'] = 1;
    $current++;
    // Overwrite the text file with the new value
    $fp = fopen($fn, 'w');
    fwrite($fp, $current);
    fclose($fp);
}
// Return the updated value
echo $current;