## Parameters:
-* Optional ```string $header_name```
+* Optional string $header_name
The key of a header to retrieve.
## Returns:
-* ```NULL```, if $header_name was not found
-* ```string```, the compound header when $header_name was found
-* ```array``` of all headers if $header_name was not specified
+* NULL, if $header_name was not found
+* string, the compound header when $header_name was found
+* array of all headers if $header_name was not specified