Fix #672 Handle passing-by-reference in native PHP functions

src/main/php/PHPMD/Rule/CleanCode/UndefinedVariable.php

@@ -17,6 +17,7 @@
 
 namespace PHPMD\Rule\CleanCode;
 
+use PDepend\Source\AST\ASTArguments;
 use PDepend\Source\AST\ASTArray;
 use PDepend\Source\AST\ASTClass;
 use PDepend\Source\AST\ASTPropertyPostfix;
@@ -31,6 +32,8 @@
 use PHPMD\Rule\AbstractLocalVariable;
 use PHPMD\Rule\FunctionAware;
 use PHPMD\Rule\MethodAware;
+use ReflectionException;
+use ReflectionFunction;
 
 /**
  * This rule collects all undefined variables within a given function or method
@@ -77,9 +80,36 @@ public function apply(AbstractNode $node)
                 $this->addVariableDefinition($variable);
             }
 
-            if (!$this->checkVariableDefined($variable, $node)) {
-                $this->addViolation($variable, array($this->getVariableImage($variable)));
+            $this->doCheckVariable($variable, $node);
+        }
+    }
+
+    private function doCheckVariable($variable, $node)
+    {
+        if (!$this->checkVariableDefined($variable, $node)) {
+            $parent = $this->getNode($variable->getParent());
+
+            if ($parent && $parent instanceof ASTArguments) {
+                $argumentPosition = array_search($this->getNode($variable), $parent->getChildren());
+                $function = $this->getNode($parent->getParent());
+                $functionName = $function->getImage();
+
+                try {
+                    $reflectionFunction = new ReflectionFunction($functionName);
+                    $parameters = $reflectionFunction->getParameters();
+
+                    if ($parameters[$argumentPosition]->isPassedByReference()) {
+                        $this->addVariableDefinition($variable);
+
+                        return;
+                    }
+                } catch (ReflectionException $exception) {
+                    // @TODO: Find a way to handle user-land functions
+                    // @TODO: Find a way to handle methods
+                }
             }
+
+            $this->addViolation($variable, array($this->getVariableImage($variable)));
         }
     }