Trim string from left and from right

How can I trim 5 characters from a string from left and right side. e.g.

4k2l3k4jc9l3kancie9

What should be trimmed and kept are:

4k2l3      k4jc9l3ka     ncie9
  ^            ^           ^
remove        keep      开发者_如何转开发 remove

$string = substr($string, 5, -5);

$string = substr($string, 5, -5);//from left
$string = substr($string, 0, 5);//from right