$re = '/^(\d+-\d+-\d+)_(\d+:\d+:\d+)\.\d+_(\d+)_\d+_(\d+)\.jpg$/';
$str = '2019-12-05_18:02:28.801656_104_1_1575549141338.jpg';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($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