$re = '/(COM-)(ALM\d{1,2}_)(BIT$|BIT\D.*|(?!BIT)\D.*)/m';
$str = 'COM-ALM2_BIT_1
COM-ALM2_BIT
COM-ALM2_AZIrgendwas_1
COM-ALM3_NameBIT
COM-ALM3_BITName
COM-ALM3_Name
COM-ALM2_BIT1
COM-ALM2_BIT15
COM-ALM11_BIT7
COM-ALM11_BIT11
OM-ALM_BIT1
COM-ALM_Name';
preg_match_all($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