$re = '/^.*(win(dows)?|r(hel|edhat)).*$/im';
$str = 'win-abc123
def456-windows
123123-WIN-ghi789
rhel-jkl012
45u8234dgf-redhat-mno345
pqr678-RHEL';
preg_match_all($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