$re = '/^(?:(?<timestamp>[^|]+)\|(?<severity>[^|]+)\|(?<x>[^|]+)\|(?<y>[^|]+)\|(?<a>[^|]+)\|(?<b>[^|]+)\|(?<c>[^|]+)(?:\|(?<d>[^|]+))?)$/m';
$str = ' 2017-12-19 09:39:41|INFO|4b483c4b138de23b2f83a208c2313c4a|8de3f071aed6401d9ff5c4289694e852|a|b|c
2017-12-19 09:39:41|ERRO|4b483c4b138de23b2f83a208c2313c4a|8de3f071aed6401d9ff5c4289694e852|a|b|c|d';
preg_match_all($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