$re = '~^(?!19)([^:\n]+).*~m';
$str = 'rs1231243:G:T:0
rs483294:C:T:5098723
19:4783234:T:G
rs19873423:A:C
19:83947355:C:T
kpg897324
rs3287492:G:C';
preg_match_all($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