jetzt sieht es so aus:
<?php
error_reporting(E_All);
/*chmod("img.txt", 0777);
$file = "img.txt";
$data = fopen($file, "r");
$img = fread($data, filesize($file));
fclose($data);
$new = $img++;
if($new==37){
$new = 1;
}
$data = fopen($file, "w+");
fwrite($data, $new);
fclose($data);*/
$img = file_get_contents("img.txt");
echo "<img src=\"images/preview/".$img.".bmp\">";
$new = $img++;
file_put_contents("img.txt", $new);
?>
...und funzt immer noch nicht...