initial commit of validation classes.

system/validation/rules/with_callback.php

@@ -0,0 +1,48 @@
+<?php namespace System\Validation\Rules;
+
+use System\Validation\Rule;
+
+class With_Callback extends Rule {
+
+	/**
+	 * The callback.
+	 *
+	 * @var function
+	 */
+	public $callback;
+
+	/**
+	 * Evaluate the validity of an attribute.
+	 *
+	 * @param  string  $attribute
+	 * @param  array   $attributes
+	 * @return void
+	 */
+	public function check($attribute, $attributes)
+	{
+		if ( ! array_key_exists($attribute, $attributes))
+		{
+			return true;
+		}
+
+		if ( ! is_callable($this->callback))
+		{
+			throw new \Exception("A validation callback for the [$attribute] attribute is not callable.");
+		}
+
+		return call_user_func($this->callback, $attributes[$attribute]);
+	}
+
+	/**
+	 * Set the validation callback.
+	 *
+	 * @param  function  $callback
+	 * @return With_Callback
+	 */
+	public function using($callback)
+	{
+		$this->callback = $callback;
+		return $this;
+	}
+
+}