$re = '/\d+(?=,\d*\s*CZK)/m';
$str = 'Date: Sat, 13 Jun 2015 13:26:05 +0100
Subject: Changing the balance: +50,00 CZK
Dear client,
Date: Sat, 14 Jun 2015 14:58:05 +0100
Subject: Changing the balance: +75,00 CZK
Dear client,';
preg_match_all($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