Here's an alternative solution using DateTime:-
function datediffInWeeks($date1, $date2)
{
if($date1 > $date2) return datediffInWeeks($date2, $date1);
$first = DateTime::createFromFormat('m/d/Y', $date1);
$second = DateTime::createFromFormat('m/d/Y', $date2);
return floor($first->diff($second)->days/7);
}
var_dump(datediffInWeeks('1/2/2013', '6/4/2013'));// 21
See it working
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