Ja te batice ne kontam:
Kôd:
$in = 'test [img ]http://images.businessweek.com/ss/06/07/top_brands/image/bmw.jpg[/img] test';
$out = preg_replace('/\[img\](.*)\[\/img\]/iU', '<img src="$1"/>', $in);
echo $out;
// ovo daje
// test <img src="http://images.businessweek.com/ss/06/07/top_brands/image/bmw.jpg"/> test
Koji je tu problem?!