There are 2 special data types in PHP
Resource Data type:
It refers the external resources like database connection, FTP connection, file pointers, etc. In simple terms, a resource is a special variable which carrying a reference to an external resource.
Null Data Type:
A variable of type Null is a variable without any data. In PHP, null is not a value, and we can consider it as a null variable based on 3 condition.