PHP to obtain the http request header information

How PHP obtains the http request header information is an urgent solution and does not know how to choose. I have collected and sorted it out. the following PHP Manual provides ready-made functions:
Getallheaders
(PHP 4, PHP 5)
Getallheaders-Fetch all HTTP request headers
Description
Array getallheaders (void)
Fetches all HTTP headers from the current request.
This function is an alias for apache_request_headers (). Please read theapache_request_headers () documentation for more information on how this function works.
Return value
An associative array of all the HTTP headers in the current request, orFALSE on failure.
Example #1 getallheaders () example
The code is as follows:
Foreach (getallheaders () as $ name => $ value ){
Echo "$ name: $ value \ n ";
}
?>

However, this function can only be used in an apache environment. iis or nginx does not support this function. it can be implemented through a custom function.
The code is as follows:
If (! Function_exists ('getallheaders '))
{
Function getallheaders ()
{
Foreach ($ _ SERVER as $ name => $ value)
{
If (substr ($ name, 0, 5) = 'http _')
{
$ Headers [str_replace ('', '-', ucwords (strtolower (str_replace ('_','', substr ($ name, 5)] = $ value;
}
}
Return $ headers;
}
}
?>

Okay. let's see what's printed.
The code is as follows:
Print_r (getallheaders ());

Result:
The code is as follows:
Array
(
[Accept] => */*
[Accept-Language] => zh-cn
[Accept-Encoding] => gzip, deflate
[User-Agent] => Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0;. net clr 2.0.50727)
[Host] => localhost
[Connection] => Keep-Alive
)