This title is not very strict, it should be said that you can use the dot number of the cookie name, but will be converted, you name a cookie:
$_cookie[' my.name '] = 1;
You can't actually find this value in a cookie by ' my.name ', Only ' my_name ':
echo $_cookie[' My_name '];
PHP has been automatically converted for you, and the period turns to underline.
Why does PHP do this? This is because $_get/$_post/$_server/$_cookie ... The values of these global functions, in many previous versions, can be accessed directly locally via the register_globals parameter, such as when register_globals = On is opened, and the access $my_name takes a direct value of 1. If it is $my.name, then does not conform to the PHP variable naming principle, this is not just a period (.) The problem.
Therefore, the naming of $_cookie has already met the PHP naming standard.
Opening register_globals is a bad decision because it may overwrite the original values in the script, such as:
$uc _is_login = true;
Users only need to send a url?a=1 HTTP request can be logged by default. This is a very dangerous practice and should be turned off. In fact, PHP6 has removed this option.