php : result of sum array values is wrong

php : result of sum array values is wrong

I have an array:
$test =array('49'=> '-0','51'=> '-0','50'=> '0','53'=> '-1.69','55'=>
'0','57'=> '-2','59'=> '-6','60'=> '-12','65'=> '0','66'=> '0','67'=>
'21.69','69'=> '0','70'=> '0','71'=> '0',);
echo "\n".'===== First Method ========';
echo "\n\n".print_r($test);
echo "\n array_sum: ".array_sum($test);
echo "\n\n".'===== Second Method ========';
$total = 0;foreach($test as $value) $total += $value;
echo "\n foreach:".$total."\n";
the result is

it is wrong, the result should be 0, not 3.5527136788E-15, how to fix it ?