unique hit counter p1

<?php
    $filename = 'counter.txt';
    $ip_filename = 'ip.txt';

    function inc_count() {
        $ip = $_SERVER['REMOTE_ADDR'];
        global $filename, $ip_filename;

        $current_value = (file_exists($filename)) ? file_get_contents($filename) : 0 ;

        file_put_contents($filename, ++$current_value);
    }

    inc_count();

?>