Update UniqueObject Validator docs

Add php usage and correct some English

Resources/doc/unique_object_validator.markdown

@@ -1,24 +1,79 @@
 The UniqueObjectValidator
 =========================
 
-In a form, if you want to validate the unicity of a field in a table you have to use the `UniqueObjectValidator`.
-The only way to use it is in a `validation.yml` file, like this:
+In a form, if you want to validate the uniqueness of a field in a table you have to use the `UniqueObjectValidator`.
+
+You may use as many validators of this type as you want.
+
+YAML
+----
+
+You can specify this using the `validation.yml` file, like this:
 
 ``` yaml
 Acme\DemoBundle\Model\User:
     constraints:
         - Propel\PropelBundle\Validator\Constraints\UniqueObject: username
 ```
 
-For validate the unicity of more than just one fields:
+If you want to validate the uniqueness of more than just one field:
 
 ``` yaml
 Acme\DemoBundle\Model\User:
     constraints:
         - Propel\PropelBundle\Validator\Constraints\UniqueObject: [username, login]
 ```
 
-As many validator of this type as you want can be used.
+PHP
+---
+
+You can also specify this using php. Fields can be specified as a string if there is only one field
+
+``` php
+use Propel\PropelBundle\Validator\Constraint\UniqueObject;
+
+...
+
+    /**
+     * Load the Validation Constraints
+     *
+     * @param ClassMetadata $metadata
+     */
+    public static function loadValidatorMetadata(ClassMetadata $metadata)
+    {
+        $metadata->addConstraint(
+            new UniqueObject(
+                array(
+                    'fields' => 'username',
+                    'message' => 'We already have a user with {{ fields }}'
+                )
+            )
+        );
+    }
+```    
+
+If there is more than one field you must use an array
+
+``` php
+
+...
+
+        $metadata->addConstraint(
+            new UniqueObject(
+                array(
+                    'fields' => array('username', 'login')
+                    'message' => 'We already have a user with {{ fields }}'
+                )
+            )
+        );
+
+...
+
+```
+
+
+
+
 
 
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