Add an abstraction for a virtual command that leverages Redis scripting with the new EVAL command.

lib/Predis/Commands/ScriptedCommand.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Predis\Commands;
+
+abstract class ScriptedCommand extends ServerEval {
+    public abstract function getScript();
+
+    public abstract function keysCount();
+
+    protected function filterArguments(Array $arguments) {
+        if (($keys = $this->keysCount()) === -1) {
+            $keys = count($arguments);
+        }
+        return array_merge(array($this->getScript(), $keys), $arguments);
+    }
+}