如何计算内部数组计数

I have an array like as

我有一个类似的数组

$arr[0] = 'summary';
$arr[1]['contact'][] = 'address1';
$arr[1]['contact'][] = 'address2';
$arr[1]['contact'][] = 'country';
$arr[1]['contact'][] = 'city';
$arr[1]['contact'][] = 'pincode';
$arr[1]['contact'][] = 'phone_no';
$arr[2]['work'][] = 'address1';
$arr[2]['work'][] = 'address2';
$arr[2]['work'][] = 'country';
$arr[2]['work'][] = 'city';
$arr[2]['work'][] = 'pincode';
$arr[2]['work'][] = 'phone_no';
$arr[0] =