新人提问：居然输出一片空白

新人提问：竟然输出一片空白

Provide up to six keywords that you believe best describe the state in
which you live:

Keyword 1:

Keyword 2:

Keyword 3:

Keyword 4:

Keyword 5:

Keyword 6:

index.php:
function sanitize_data(&$value, $key) {
$value = strip_tags($value);
}

array_walk($_POST['keyword'], "sanitize_data");
?>

输入数据后提交转到index.php输出竟然一片空白。。。。为什么呢？完全不关单引号双引号的事！

------解决方案--------------------
是不是要加个echo