$string = preg_replace_callback("#\[img\]\s*((http://|https://|www\.)[A-Za-z0-9-_\./\?\%\&\+\;\,~=]+?)\s*\[/img\]#is",

                create_function('$matches', 'global $fm; $matches[1] = ($matches[2] === "www.") ? "http://".$matches[1] : $matches[1];

				                return ($fm->exbb[\'imgpreview\'] === TRUE) ? replace_img_link($matches[1]) : "<img src=\"".$matches[1]."\"> ";'),$string);