$re = '/\b(?:YV[^\W_]{8}|S?VNA[^\W_]{5})\b/m';
$str = 'There are four serial numbers in here: ;YV12345678. VNA1234A and ,VNAB4321 or :SVNA12345 here and a couple that won\'t be of interest YV123456789 VNA123456 or SVNA1234
2020-03-24 15:47:46 - (Work notes) Monitor, wired keyboard/mouse SVNA3L3A0 picked up equipment 2020-03-16 08:51:04 - (Work notes) Hello, I see that the monitor part of your ticket is incomplete. Update me with this information.';
preg_match_all($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