Fixes #477: support multi reverse proxy with comma syntax

Going through multiple reverse proxy will store multiple scheme and port in HTTP header separated by a comma. Shaarli will use the first one to generate server_url.

application/HttpUtils.php

@@ -106,12 +106,22 @@ function server_url($server)
     // Shaarli is served behind a proxy
     if (isset($server['HTTP_X_FORWARDED_PROTO'])) {
         // Keep forwarded scheme
+        if (strpos($server['HTTP_X_FORWARDED_PROTO'], ',') !== false) {
+            $schemes = explode(',', $server['HTTP_X_FORWARDED_PROTO']);
+            $scheme = trim($schemes[0]);
+        } else {
             $scheme = $server['HTTP_X_FORWARDED_PROTO'];
+        }
 
         if (isset($server['HTTP_X_FORWARDED_PORT'])) {
             // Keep forwarded port
+            if (strpos($server['HTTP_X_FORWARDED_PORT'], ',') !== false) {
+                $ports = explode(',', $server['HTTP_X_FORWARDED_PORT']);
+                $port = ':' . trim($ports[0]);
+            } else {
                 $port = ':' . $server['HTTP_X_FORWARDED_PORT'];
             }
+        }
 
         return $scheme.'://'.$server['SERVER_NAME'].$port;
     }

tests/HttpUtils/ServerUrlTest.php

@@ -67,6 +67,19 @@ public function testHttpsProxyForward()
                 )
             )
         );
+
+        $this->assertEquals(
+            'https://host.tld:4974',
+            server_url(
+                array(
+                    'HTTPS' => 'Off',
+                    'SERVER_NAME' => 'host.tld',
+                    'SERVER_PORT' => '80',
+                    'HTTP_X_FORWARDED_PROTO' => 'https, https',
+                    'HTTP_X_FORWARDED_PORT' => '4974, 80'
+                )
+            )
+        );
     }
 
     /**