$re = '/Amount:\K\d+/';
$str = 'Date:21 Month:03 Year:2017 Amount:50 Category:Grocery Account:bank Note:expensive
Date:1 Month:04 Year:2017 Amount:150 Category:Grocery Account:bank Note:expensive
Date:14 Month:04 Year:2017 Amount:5 Category:Grocery Account:bank Note:expensive
Date:28 Month:04 Year:2017 Amount:5935 Category:Grocery Account:bank Note:expensive';
preg_match_all($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