added Dibi\Expression [Closes #264]

src/Dibi/Expression.php

@@ -0,0 +1,32 @@
+<?php
+
+/**
+ * This file is part of the "dibi" - smart database abstraction layer.
+ * Copyright (c) 2005 David Grudl (https://davidgrudl.com)
+ */
+
+namespace Dibi;
+
+
+/**
+ * SQL expression.
+ */
+class Expression
+{
+	use Strict;
+
+	/** @var array */
+	private $values;
+
+
+	public function __construct()
+	{
+		$this->values = func_get_args();
+	}
+
+
+	public function getValues()
+	{
+		return $this->values;
+	}
+}

src/Dibi/Translator.php

@@ -458,6 +458,9 @@ final class Translator
 		} elseif ($value instanceof Literal) {
 			return (string) $value;
 
+		} elseif ($value instanceof Expression) {
+			return call_user_func_array([$this->connection, 'translate'], $value->getValues());
+
 		} else {
 			$type = is_object($value) ? get_class($value) : gettype($value);
 			return $this->errors[] = "**Unexpected $type**";