Question

Why Cookies doesn’t store information in php ?

even in this simple code ..

<?
   setcookie("test","Cookies teso");
   echo "My cookie value: ".$_COOKIE["test"];
?>

Answer 1

They will be available on the next page load. From the documentation:

Cookies will not become visible until the next loading of a page that
the cookie should be visible for. To test if a cookie was successfully
set, check for the cookie on a next loading page before the cookie
expires. Expire time is set via the expire parameter. A nice way to
debug the existence of cookies is by simply calling
print_r($_COOKIE);.

Note that you need to set the cookies before any other script output is done:

Like other headers, cookies must be sent before any output from your
script (this is a protocol restriction). This requires that you place
calls to this function prior to any output, including and
tags as well as any whitespace.