Include parent keyword as static reference (#44)

* Tests: add test for `parent::` variable reference

* Include T_PARENT in list of static references

Author: sirbrillig

VariableAnalysis/Sniffs/CodeAnalysis/VariableAnalysisSniff.php

@@ -364,6 +364,7 @@ protected function checkForStaticMember(File $phpcsFile, $stackPtr, $varName, $c
     $staticReferences = [
       T_STRING,
       T_SELF,
+      T_PARENT,
       T_STATIC,
     ];
     if (! in_array($tokens[$classNamePtr]['code'], $staticReferences, true)) {

VariableAnalysis/Tests/CodeAnalysis/fixtures/ClassWithMembersFixture.php

@@ -63,3 +63,10 @@ static function method_with_late_static_binding($param) {
         static::some_method(static::CONSTANT, $param);
     }
 }
+
+class ChildClassWithMembers extends ClassWithMembers {
+    function method_with_parent_reference() {
+        echo self::$static_member_var;
+        echo parent::$no_such_static_member_var;
+    }
+}