Description:
------------
The built-in CLI web server does not support getallheaders(). Given that projects may need to support headers unavailable in $_SERVER and that both Apache and FastCGI support it, it is unfortunate that the CLI web server does not.

I expect this would not be difficult to implement, considering that the CLI web server likely already has this information at its disposal.

Test script:
---------------
<?php
// The header() is just so that var_dump()'s output looks good in browser
// I'm aware that getallheaders() gets *request* headers
header('Content-Type: text/plain');
var_dump(getallheaders());

Expected result:
----------------
array(0) {
  ...
}

Actual result:
--------------
<br />
<b>Fatal error</b>:  Call to undefined function getallheaders() in <b>D:\Projects\test.php</b> on line <b>3</b><br />