Something

<?
$myFile = "testFile.txt";
$fh = fopen($myFile, 'r+');
$theData = (int) fgets($fh);

$stringData = $theData + 1;
fseek($fh, 0);
fwrite($fh, $stringData);

fclose($fh);



$num = (int) $HTTP_GET_VARS['n'];
$num++;
if ($num > 2500){
$num = 2500;
}