$re = '/,?[^u][^k]:\d+,\d+,\w,\w+,\w+/';
$str = 'ro:2581,1309531682152,A,Place,Page,me:2642,1310989368864,A,Place,Page,uk:2556,1309267095061,A,Place,Page,me:2642,1310989380238,D,Place,Page,me:2642,1334659643627,D,Place,Page,ro:3562,1378721526696,A,Place,Page,uk:1319,1309337246675,D,Place,Page,ro:2581,1379500694666,D,Place,Page,uk:1319,1309337246675,A,Place,Page';
$subst = "";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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