How to get rid of PHP Notice: Undefined index: HTTPS in X on line 123 -

I just found out that I have thousands of errors, coming from two files.

I've removed many errors using the isset , but I can not understand how to remove the last two errors. Maybe you guys can help me.

  PHP Notice: The first PHP file from the code HTTPS   
 at line 123 on / 123x / xxx / xxx.php which generates errors :  
  function curPageURL () {$ pageURL = 'http'; If ($ _SERVER ["HTTPS"] == "on") {$ pageURL} = "S";} $ pageURL. = ": //"; If ($ _SERVER ["SERVER_PORT"]! = "80") {$ pageURL = $ _SERVER ["SERVER_NAME"] ":". $ _ SERVER ["SERVER_PORT"]. $ _ Server ["REQUEST_URI"]; } And {$ pageURL = $ _SERVER ["SERVER_NAME"] $ _ Server ["REQUEST_URI"]; } $ PageURL; }   
 more accurate this line:  
  if $$ ($ {_SERVER ["HTTPS"] == "on") {$ pageURL} = "S";}   
 and  
  if (isset ($ tag)) {$ tag = htmlspecialchars ($ _ request ['tag'] , ENT_QUOTES); }    
 
 
 You can change:  
  ($ _SERVER ["HTTPS"] == "ON") {$ pageURL} = ("HTTPS ', $ _SERVER) and $ _SERVER [" HTTPS "] == "at") {$ pageURL} = "S";}   
 gives a bullion as I see it first and & amp; Amp; If the statement exits before checking the value of $ _SERVER ["HTTPS"], then it does not exist.