$re = '/^\w{3,16}$/mi';
$str = 'awesome
1232443242
34
45453.54
1
2
3342
43543
.co
coo
niceee
minecraftGamer23
co
_nicelol23__
T_T
1.2e3
awo!d
awesome';
preg_match_all($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