<?php
function createThumb($source,$dest) {

    $thumb_size = 150;

    $size = getimagesize($source);
    $width = $size[0];
    $height = $size[1];

    if($width> $height) {
        $x = ceil(($width - $height) / 2 );
        $width = $height;
    } elseif($height> $width) {
        $y = ceil(($height - $width) / 2);
        $height = $width;
    }

    $new_im = ImageCreatetruecolor($thumb_size,$thumb_size);
    $im = imagecreatefromjpeg($source);
    imagecopyresampled($new_im,$im,0,0,$x,$y,$thumb_size,$thumb_size,$width,$height);
    imagejpeg($new_im,$dest,100);

}
?>