$re = '/.*\w{8}-\w{4}-\w{4}-\w{4}-\w{12}\s*:\s*com.netflix.hystrix.exception.HystrixRuntimeException:\s*(?<error>.*?)\s*(\.|$)/m';
$str = '2021-02-22 00:58:30,255 ERROR [com.xxx.yyy.interfaces.exceptions.web.ServerErrorController] (ajp-/100.10.100.100:8000-10) Unexpected failure: GET /yyy/api/zzz/aaa 500 - User: 1XX1XX1X-1X11-1111-1X11-111X11111111: com.netflix.hystrix.exception.HystrixRuntimeException: Error message.';
preg_match_all($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