Prefer apache_request_headers when reading request headers.

Apache does not pass the Authorization header through to PHP as
$_SERVER["HTTP_AUTHORIZATION"], so reading from $_SERVER is not viable
with Apache.

.idea/php.xml

@@ -1,5 +1,3 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
+<project version="4" />
-  <component name="PhpProjectSharedConfiguration" php_language_level="5.3.0" />
-</project>
 

src/pjdietz/WellRESTed/Request.php

@@ -91,6 +91,11 @@ class Request extends Message implements RequestInterface
      */
     public static function getRequestHeaders()
     {
+        // Prefer apache_request_headers is available.
+        if (function_exists('apache_request_headers')) {
+            return apache_request_headers();
+        }
+
         // http://www.php.net/manual/en/function.getallheaders.php#84262
         $headers = array();
         foreach ($_SERVER as $name => $value) {

test/ApacheRequestHeadersTest.php

@@ -0,0 +1,24 @@
+<?php
+
+// This file must be in the global namespace to add apache_request_headers
+
+use pjdietz\WellRESTed\Request;
+
+class ApacheRequestHeadersTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @runInSeparateProcess
+     * @preserveGlobalState disabled
+     */
+    public function testReadApacheRequestHeaders()
+    {
+        if (!function_exists('apache_request_headers')) {
+            function apache_request_headers() {
+                return array();
+            }
+        }
+
+        $headers = Request::getRequestHeaders();
+        $this->assertNotNull($headers);
+    }
+}