[HaBo]

 <?php
header("Content-type: image/jpeg";);

$file= "$BILD";
$path= "images";
$filepath = $path."/".$file;
if(file_exists("$filepath";)) {
// Originalbild einlesen
$h_img= imagecreatefromjpeg("$path/$file";);
$width= imagesx($h_img);
$height= imagesy($h_img);

// Thumbnail im Speicher erzeugen
$thb_x= $X;
$thb_y= $Y;
$h_thb= imagecreate($thb_x, $thb_y);

// Verkleinern
imagecopyresized(
$h_thb,
$h_img,
0,
0,
0,
0,
$thb_x,
$thb_y,
$width,
$height
);

// In File speichern
imagejpeg($h_thb, "$file",100);

// Aufräumen
imagedestroy($h_thb);
imagedestroy($h_img);
}

// Ausgabe
readfile("$file";);
?>

if(file_exists("$filepath";)) {
$h_img= imagecreatefromjpeg("$path/$file";);
readfile("$file";);