Description:
------------
substr_replace accepts arguments not only as strings but as arrays, and judging from SVN it is there for many years, but the manual says nothing about this option. 

Test script:
---------------
var_dump(substr_replace(array("foo","bar"),array("baz","blah"),array(1,2)));

Actual result:
--------------
array(2) {
  [0]=>
  string(4) "fbaz"
  [1]=>
  string(6) "bablah"
}