$re = '/(?:[^\s][^\s]+\s){2}(?P<field1>[^\s]+(?:\s\w+)?)\s\d+\s+</';
$str = '<37> 1 2018-04-23T08:08:08Z E876876876 auth 0 <login> [kdnckn rrgrr]
<37> 1 2018-04-23T08:08:08Z E876876876 SECURE AUDIT 0 <secure audit error> [cdkncdckne dckmdkcmd]
';
preg_match_all($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