Start of factor graph port. Things don't work yet, but a lot of syntax updates towards PHP

PHPSkills/FactorGraphs/Variable.php

@@ -0,0 +1,71 @@
+<?php
+namespace Moserware\Skills\FactorGraphs;
+
+class Variable
+{
+    private $_name;
+    private $_prior;
+    private $_value;
+
+    public function __construct($name, $prior)
+    {
+        $this->_name = "Variable[" . $name . "]";
+        $this->_prior = $prior;
+        $this->resetToPrior();
+    }
+
+    public function getValue()
+    {
+        return $this->_value;
+    }
+
+    public function setValue($value)
+    {
+        $this->_value = $value;
+    }
+
+    public function resetToPrior()
+    {
+        $this->_value = $this->_prior;
+    }
+
+    public function __toString()
+    {
+        return $this->_name;
+    }
+}
+
+class DefaultVariable extends Variable
+{
+    public function __construct()
+    {
+        parent::__construct("Default", null);
+    }
+
+    public function getValue()
+    {
+        return null;
+    }
+
+    public function setValue($value)
+    {
+        throw new Exception();
+    }
+}
+
+class KeyedVariable extends Variable
+{
+    private $_key;
+    public function __construct($key, $name, $prior)
+    {
+        parent::__construct($name, $prior);
+        $this->_key = $key;
+    }
+
+    public function getKey()
+    {
+        return $this->_key;
+    }
+}
+
+?>