$re = '/\[IMG\]http:\/\/i64\.tinypic\.com\/(.*?)\[\/IMG\]/i';
$str = '[IMG]http://i64.tinypic.com/2zgg086.jpg[/IMG]
[IMG]http://i64.nottinypic.com/2zgg086.jpg[/IMG]
[IMG]http://i64.tinypic.com/2zgg0cdsc86.jpg[/IMG]
[img]http://i64.tinypic.com/2zgg086.jpg[/IMG]
';
preg_match_all($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