$ _ SERVER ['Local _ ADDR '] and $ _ SERVER ['server _ ADDR'] are error messages?

$ _ SERVER ['Local _ ADDR '] and $ _ SERVER ['server _ ADDR ?? You can see this code in the PHP file of a website Program: $ md5str = ('ehtaziyt '. $ ep ). $ _ SERVER ['server _ ADDR ']). $ _ SERVER ['lo $ _ SERVER ['Local _ ADDR '] and $ _ SERVER ['server _ ADDR ??
You can see this code in the PHP file of a website Program: $ md5str = ('ehtaziyt '. $ ep ). $ _ SERVER ['server _ ADDR ']). $ _ SERVER ['Local _ ADDR ']). '22. 90h7 ^ aaz0 (! SkZnmLa03 # nVAc_f (h-!) Wsx ~ 9dlP1% uXJnB8.65E3zYYwa '); but when I run some code segments, the following error message Notice: Undefined index is displayed. Indicates that $ _ SERVER ['Local _ ADDR '] and $ _ SERVER ['server _ ADDR'] are invalid variables. Excuse me: $ _ SERVER ['Local _ ADDR '] and $ _ SERVER ['server _ ADDR'] are nothing. I have not checked the php Manual, but this code appears in the commercial program. it has been running for several years and should not be wrong.
Please let me know.

------ Solution --------------------
"SERVER_ADDR"
The IP address of the server where the script is currently running.
"REMOTE_ADDR"
Browsing the IP address of the user on the current page.
LOCAL_ADDR does not know what it is. it is estimated that it was added by itself.
------ Solution --------------------
$ _ SERVER ['Local _ ADDR '] is no longer available in PHP5