Timestamp in int or string memory consumption

test.php

$mx = 10000;
$mem = memory_get_usage();
$data1 = array();
$i = $mx;
while ($i-- >0) {
	$data1[] = 1368118712;
}
$i1 = (memory_get_usage() - $mem);

echo ' ';

$mem = memory_get_usage();
$data2 = array();
$i = $mx;
while ($i-- >0) {
	$data2[] = '1368118712';
}
$i2 = (memory_get_usage() - $mem);

echo $i2/$i1;

echo ' ';

echo count($data1);
echo ' ';
echo count($data2);