Variable in uppercase?

I defined a variable accessDate and the snippet is shortcode but not php code.

I used the snippet but where accessDate is used is blank. Just want to know whether upper case variable is supported or not.

screenshot:

https://lh5.googleusercontent.com/-fAuOWkTPVJE/VKjr2Bmki-I/AAAAAAAAEg0/O4_YvoZRFK4/s800/%25E6%258D%2595%25E8%258E%25B7.JPG

https://lh6.googleusercontent.com/-sqDZI7zpfLE/VKjr1-AKOZI/AAAAAAAAEgs/BV4njm4NSSg/s800/2.JPG

https://lh6.googleusercontent.com/-rzSgPlYhqmk/VKjr1_HKo2I/AAAAAAAAEg4/8I98aADaOxw/s800/3.JPG

https://ww.wp.xz.cn/plugins/post-snippets/