We can pass by reference the values in an array to modify the array. But in the following code snippet, the output will be somewhat erratic.  

$someArray = array(1,2,3);
foreach($someArray as &$value) {
   $value++;
}

$value++;
print_r($value);

The output is

array(2,3,5)

As you noticed the last value is incremented twice, because the reference is not lost after the loop ends. The increment $value++ outside the loop will update the last reference viz the last element. To avoid this one must unset your last used reference

$someArray = array(1,2,3);
foreach($someArray as &$value) {
   $value++;
}

unset($value);
$value++;
print_r($value);

Now the output will be

array(2,3,4)