$re = '/(?<= (?:55|270|271)=)[^ ]+/';
$str = '20220606-21:10:21.930 : 8=FIX.4.49=209 35=W34=35 49=FIXDIRECT.FT 52=20220606-21:10:21.925 56=MM_EUR_FIX_QS 55=US30 262=96 268=2 269=0 270=32921.6 271=2000000 299=16ynjsz-16ynjsz5qCaA 269=1 270=32931.4 271=2000000 299=16ynjsz-16ynjsz5qCaA 10=048';
preg_match_all($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