$re = '/^[A-Z]\d{2}(?:\.\d{1,2}|\d{0,2})$/m';
$str = 'D99
M00.0
M01.6
J98.3
T05.0
M96.81
D68.20
D3412
D34.
9D.0
6G
7H.
M96.811
J234.82
G687.1
GU87.11';
preg_match_all($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