怎么判断每组数组里有多少个正数和负数

$arr=array(  array('3','-1','4','2','-2'),  array('-3','-1','-4','-12','-2','21','13','-16'),  array('-5','-8','4','2'));foreach($arr as $k=>$a) {  $n = count(array_keys(array_map('sign',$a), -1));  $r[$k] = array('+' => count($a) - $n, '-' => $n);}print_r($r);function sign($n) {  return $n/abs($n);}