Little problem in page A, now:

I imagine I must verify if I have 'something' in $_POST
(I get an Undefined Variable notice when I directly write:

if($_POST[$k]!=''){
${$k}=$v;
}

and I access this page for the first time, that is when for sure there
is nothing in $_POST
)

I tried
if(array_key_exists(etc. but this way I must write code for any
possible key...

Is there a handy way to know if there is 'something' in $_POST?

Thanks!