Description:
------------
exec() doesn't return empty lines from execution results as empty strings, but as newline characters.

Test script:
---------------
cmd.php:

#!/usr/bin/env php
Line one
Line two

Line three
Line four

test.php:

<?php
exec(__DIR__ . '/cmd.php', $result, $value);
var_dump($result);


Expected result:
----------------
array(5) {
  [0]=>
  string(8) "Line one"
  [1]=>
  string(8) "Line two"
  [2]=>
  string(0) ""
  [3]=>
  string(10) "Line three"
  [4]=>
  string(9) "Line four"
}


Actual result:
--------------
array(5) {
  [0]=>
  string(8) "Line one"
  [1]=>
  string(8) "Line two"
  [2]=>
  string(1) "
"
  [3]=>
  string(10) "Line three"
  [4]=>
  string(9) "Line four"
}