Description:
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---
From manual page: http://www.php.net/function.array-sum
---
$arr = array(null,null,null);
$sum = array_sum($arr);

expected value = null
returned value = 0

Test script:
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$arr = array(null,null,null);
$sum = array_sum($arr);
echo $sum;

Expected result:
----------------
NULL

Actual result:
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0