$re = '/From\s+\d{19}@/';
$str = 'From 1489304828131889971@xxx Sat Jan 03 07:02:43 2015
From 1489220782115942636@82hs Fri Jan 02 08:46:51 2015';
preg_match_all($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