getallheaders() is an alias for apache_request_headers(). It will return an associative array of all the HTTP headers in the current request. Please read the apache_request_headers() documentation for more information on how this function works.
Note: In PHP 4.3.0, getallheaders() became an alias for apache_request_headers(). Essentially, it was renamed. This is because this function only works when PHP is compiled as an Apache Module.
See also apache_request_headers().
Note: From PHP 4.3.3 on you can use this function with the NSAPI server module in Netscape/iPlanet/SunONE webservers, too.