p = "|<[^>]+>(.*?)</[^>]+>|i";

$str = "<b>example: </b><div align=left>this is a test</div>";

preg_match_all($p, $str, $matches);

print_r($matches);

"|<[^>]+>(.*?)</[^>]+>|i";是不是</[^>里少了\？