diff --git src/wp-includes/IXR/class-IXR-client.php src/wp-includes/IXR/class-IXR-client.php
index f66bcb30d6..549e494cf6 100644
--- src/wp-includes/IXR/class-IXR-client.php
+++ src/wp-includes/IXR/class-IXR-client.php
@@ -58,9 +58,8 @@ class IXR_Client
 		self::__construct( $server, $path, $port, $timeout );
 	}
 
-    function query()
+    function query( ...$args )
     {
-        $args = func_get_args();
         $method = array_shift($args);
         $request = new IXR_Request($method, $args);
         $length = $request->getLength();
diff --git src/wp-includes/IXR/class-IXR-clientmulticall.php src/wp-includes/IXR/class-IXR-clientmulticall.php
index bc40efd771..627ab881f3 100644
--- src/wp-includes/IXR/class-IXR-clientmulticall.php
+++ src/wp-includes/IXR/class-IXR-clientmulticall.php
@@ -25,9 +25,8 @@ class IXR_ClientMulticall extends IXR_Client
 		self::__construct( $server, $path, $port );
 	}
 
-    function addCall()
+    function addCall( ...$args )
     {
-        $args = func_get_args();
         $methodName = array_shift($args);
         $struct = array(
             'methodName' => $methodName,
@@ -36,7 +35,7 @@ class IXR_ClientMulticall extends IXR_Client
         $this->calls[] = $struct;
     }
 
-    function query()
+    function query( ...$args )
     {
         // Prepare multicall, then call the parent::query() method
         return parent::query('system.multicall', $this->calls);