What is wrong with $_server[' local_addr ' and $_server[' server_addr ']?

What is $_server[' local_addr ' and $_server[' server_addr '?
See this code in a php file for a website program: $MD 5str = (((' Ehtaziyt '. $ep). $_server[' Server_addr '). $_server[' Local_addr ']). ' 22.90h7^aaz0 (!skznmla03#nvac_f (h-a!) Wsx~9dlp1%uxjnb8.65e3zyywa '); but I will always stop when I run to some code and pop up the error message notice:undefined index below. Indicates that $_server[' local_addr ' and $_server[' server_addr '] are invalid variables. Excuse me: $_server[' local_addr ' and $_server[' server_addr '] what exactly is the thing, I check the PHP manual also did not find, but this code appears in the business process, has been after several years of running test, should not be wrong.
Please know the brothers and sisters can answer the next.

------Solution--------------------
"Server_addr"
The IP address of the server where the script is currently running.
"REMOTE_ADDR"
The IP address of the user who is browsing the current page.
Local_addr don't know what it is, I think I added it myself.
------Solution--------------------
$_server[' local_addr ' has not been in the PHP5.

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