This function returns an associative array of all the HTTP headers in the current request.
Note: You can also get at the value of the common CGI variables by reading them from the environment, which works whether or not you are using PHP as an Apache module. Use phpinfo() to see a list of all of the environment variables defined this way.
This example will display all the request headers for the current request.
Note: getallheaders() is currently only supported when PHP runs as an Apache module.