$re = '/\[.*IMG.*[^\]]\]/i';
$str = '[ IMG ] http://test.test/test.jpg [ /IMG] sdfsgeg
ewye [IMG]http://test.test/test.jpg [/ IMG]ertw
rtwertewt [IMG]http://test.test/test.jpg[/IMG ]sdfweqw
erqwerwq [ img ] http://test.test/test.jpg[ / IMG ]jnljlkjljlkj';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php