What is the NULL and RESOURCE data type used for and how do I declare it?

Question

PHp data types

Answer 1

A resource is a special variable, holding a reference to an external resource e.g. when you are using fopen function or mysqli_connect and assign this into some variable, your variable will have "link" for this functions and this is called resource.

NULL value represents a variable with no value (zero is also value) -- 0 !== NULL
You can simply declare null because it is a php keyword: $nullVar = NULL;

Answer 2

thanks