Enable the Generic.CodeAnalysis.UnusedFunctionParameter sniff.

The reason why the sniff was disabled up to now was that WP uses callbacks a lot and the hooked in functions may not use all parameters passed to them.

This concern was previously raised in #382 (comment)

To this end, I've send in a PR upstream to address these concerns, which has subsequently been merged.
The adjusted version of the sniff will be released in PHPCS 2.7.2.

.travis.yml

@@ -14,7 +14,7 @@ php:
 
 env:
   - PHPCS_BRANCH=master
-  - PHPCS_BRANCH=2.7.1
+  - PHPCS_BRANCH=2.7.2
 
 matrix:
   fast_finish: true

README.md

@@ -41,7 +41,7 @@ This project is a collection of [PHP_CodeSniffer](https://github.com/squizlabs/P
 
 ### Requirements
 
-The WordPress Coding Standards require the [PHP_CodeSniffer](https://github.com/squizlabs/PHP_CodeSniffer) version **2.7.0** or higher.
+The WordPress Coding Standards require the [PHP_CodeSniffer](https://github.com/squizlabs/PHP_CodeSniffer) version **2.7.2** or higher.
 The WordPress Coding Standards are currently [not compatible with the upcoming PHPCS 3 release](https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards/issues/718).
 
 ### Composer

WordPress-Extra/ruleset.xml

@@ -36,9 +36,14 @@
 	<!-- https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards/pull/382#discussion_r29970107 -->
 	<!--<rule ref="Generic.Formatting.MultipleStatementAlignment"/>-->
 
-	<!-- Hook callbacks may not use all params -->
-	<!-- https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards/pull/382#discussion_r29981655 -->
-	<!--<rule ref="Generic.CodeAnalysis.UnusedFunctionParameter"/>-->
+	<!-- Check that functions use all parameters passed.
+		 https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards/pull/xxx -->
+	<rule ref="Generic.CodeAnalysis.UnusedFunctionParameter">
+		<properties>
+			<property name="ignore_extended_classes" value="true" />
+			<property name="allow_for_callbacks" value="true" />
+		</properties>
+	</rule>
 
 	<rule ref="WordPress-Core"/>
 

composer.json

@@ -11,7 +11,7 @@
 		}
 	],
 	"require"    : {
-		"squizlabs/php_codesniffer": "^2.7"
+		"squizlabs/php_codesniffer": "^2.7.2"
 	},
 	"minimum-stability" : "RC",
 	"support"    : {