$re = '/(?i)^(?!.*interessado: ).* CNPJ\W+(\d+\.\d+\.\d+\s?\/\d+-\s?\d+)/m';
$str = 'RECLAMADO: FOO LTDA - CNPJ: 99.999.999/9999-99
RECLAMADO: FOO FOO LTDA - CNPJ: 99.999.999/9999-99
TERCEIRO INTERESSADO: FOO FOO
TERCEIRO INTERESSADO: FOO FOO FOO FOO - CNPJ: 99.999.999/9999-99
TERCEIRO INTERESSADO: FOO FOO IT\'S A TEST - CNPJ: 99.999.999/9999-99
TERCEIRO INTERESSADO: TEST
INTERESSADO: TEST - CNPJ: 99.999.999/9999-99';
preg_match_all($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