diff --git a/hphp/runtime/base/array/array_data.cpp b/hphp/runtime/base/array/array_data.cpp
index ca9a251df..47c7b356e 100644
--- a/hphp/runtime/base/array/array_data.cpp
+++ b/hphp/runtime/base/array/array_data.cpp
@@ -253,7 +253,7 @@ void ArrayData::newFullPos(FullPos &fp) {
   fp.setContainer(this);
   fp.setNext(strongIterators());
   setStrongIterators(&fp);
-  getFullPos(fp);
+  fp.m_pos = m_pos;
 }
 
 void ArrayData::freeFullPos(FullPos &fp) {
@@ -282,16 +282,10 @@ bool ArrayData::validFullPos(const FullPos& fp) const {
   return false;
 }
 
-void ArrayData::getFullPos(FullPos &fp) {
-  assert(fp.getContainer() == (ArrayData*)this);
-  fp.m_pos = ArrayData::invalid_index;
-}
-
-bool ArrayData::setFullPos(const FullPos &fp) {
-  assert(fp.getContainer() == (ArrayData*)this);
+bool ArrayData::advanceFullPos(FullPos& fp) {
   return false;
 }
-
+    
 void ArrayData::freeStrongIterators() {
   for (FullPosRange r(strongIterators()); !r.empty(); r.popFront()) {
     r.front()->setContainer(nullptr);
diff --git a/hphp/runtime/base/array/array_data.h b/hphp/runtime/base/array/array_data.h
index a9c48863f..4f0994f22 100644
--- a/hphp/runtime/base/array/array_data.h
+++ b/hphp/runtime/base/array/array_data.h
@@ -355,18 +355,12 @@ class ArrayData : public Countable {
   virtual bool validFullPos(const FullPos& fp) const;
 
   /**
-   * Sets the specified mutable iterator to point to whatever element the
-   * array's internal cursor currently points to.
+   * Advances the mutable iterator to the next element in the array. Returns
+   * false if the iterator has moved past the last element, otherwise returns
+   * true.
    */
-  virtual void getFullPos(FullPos &fp);
-
-  /**
-   * Sets the array's internal cursor to point to whetever element the
-   * specified mutable iterator to currently points to. It is the caller's
-   * responsibility to ensure that fp.getResetFlag() is false.
-   */
-  virtual bool setFullPos(const FullPos &fp);
-
+  virtual bool advanceFullPos(FullPos& fp); 
+ 
   virtual CVarRef currentRef();
   virtual CVarRef endRef();
 
diff --git a/hphp/runtime/base/array/array_iterator.cpp b/hphp/runtime/base/array/array_iterator.cpp
index d0f48eb5e..ed3f8ace0 100644
--- a/hphp/runtime/base/array/array_iterator.cpp
+++ b/hphp/runtime/base/array/array_iterator.cpp
@@ -85,8 +85,7 @@ void ArrayIter::objInit(ObjectData *obj) {
   }
   switch (getCollectionType()) {
     case Collection::VectorType: {
-      c_Vector* vec = getVector();
-      m_version = vec->getVersion();
+      m_version = getVector()->getVersion();
       m_pos = 0;
       break;
     }
@@ -150,8 +149,7 @@ ArrayIter::~ArrayIter() {
 bool ArrayIter::endHelper() {
   switch (getCollectionType()) {
     case Collection::VectorType: {
-      c_Vector* vec = getVector();
-      return m_pos >= vec->t_count();
+      return m_pos >= getVector()->t_count();
     }
     case Collection::MapType: {
       return m_pos == 0;
@@ -160,8 +158,7 @@ bool ArrayIter::endHelper() {
       return m_pos == 0;
     }
     case Collection::PairType: {
-      c_Pair* pair = getPair();
-      return m_pos >= pair->t_count();
+      return m_pos >= getPair()->t_count();
     }
     default: {
       ObjectData* obj = getIteratorObj();
@@ -343,23 +340,14 @@ bool FullPos::advance() {
     return false;
   }
   if (container == data) {
-    data = cowCheck();
-    if (getResetFlag()) {
-      setResetFlag(false);
-      data->reset();
-    } else {
-      data->setFullPos(*this);
-      data->next();
-    }
-    data->getFullPos(*this);
-  } else {
-    data = reregister();
+    return cowCheck()->advanceFullPos(*this);
   }
+  data = reregister();
   assert(data && data == getContainer());
   assert(!getResetFlag());
   if (!data->validFullPos(*this)) return false;
-  // To match PHP-like semnatics, we need to set the internal cursor to
-  // point to the next element.
+  // To conform to PHP behavior, we need to set the internal
+  // cursor to point to the next element.
   data->next();
   return true;
 }
@@ -422,14 +410,6 @@ ArrayData* FullPos::cowCheck() {
   return data;
 }
 
-ArrayData* FullPos::getData() const {
-  assert(hasVar());
-  if (getVar()->is(KindOfArray)) {
-    return getVar()->getArrayData();
-  }
-  return nullptr;
-}
-
 ArrayData* FullPos::reregister() {
   ArrayData* container = getContainer();
   assert(getArray() != nullptr && container != getArray());
@@ -456,13 +436,12 @@ MutableArrayIter::MutableArrayIter(const Variant *var, Variant *key,
   assert(getVar());
   escalateCheck();
   ArrayData* data = cowCheck();
-  if (data) {
-    data->reset();
-    data->newFullPos(*this);
-    setResetFlag(true);
-    data->next();
-    assert(getContainer() == data);
-  }
+  if (!data) return;
+  data->reset();
+  data->newFullPos(*this);
+  setResetFlag(true);
+  data->next();
+  assert(getContainer() == data);
 }
 
 MutableArrayIter::MutableArrayIter(ArrayData *data, Variant *key,
@@ -470,16 +449,15 @@ MutableArrayIter::MutableArrayIter(ArrayData *data, Variant *key,
   m_var = nullptr;
   m_key = key;
   m_valp = &val;
-  if (data) {
-    setAd(data);
-    escalateCheck();
-    data = cowCheck();
-    data->reset();
-    data->newFullPos(*this);
-    setResetFlag(true);
-    data->next();
-    assert(getContainer() == data);
-  }
+  if (!data) return;
+  setAd(data);
+  escalateCheck();
+  data = cowCheck();
+  data->reset();
+  data->newFullPos(*this);
+  setResetFlag(true);
+  data->next();
+  assert(getContainer() == data);
 }
 
 MutableArrayIter::~MutableArrayIter() {
@@ -494,9 +472,7 @@ MutableArrayIter::~MutableArrayIter() {
 }
 
 bool MutableArrayIter::advance() {
-  if (!this->FullPos::advance()) {
-    return false;
-  }
+  if (!this->FullPos::advance()) return false;
   ArrayData* data = getArray();
   assert(data);
   assert(!getResetFlag());
@@ -517,28 +493,26 @@ MArrayIter::MArrayIter(const RefData* ref) {
   assert(hasVar());
   escalateCheck();
   ArrayData* data = cowCheck();
-  if (data) {
-    data->reset();
-    data->newFullPos(*this);
-    setResetFlag(true);
-    data->next();
-    assert(getContainer() == data);
-  }
+  if (!data) return;
+  data->reset();
+  data->newFullPos(*this);
+  setResetFlag(true);
+  data->next();
+  assert(getContainer() == data);
 }
 
 MArrayIter::MArrayIter(ArrayData *data) {
   m_var = nullptr;
-  if (data) {
-    assert(!data->isStatic());
-    setAd(data);
-    escalateCheck();
-    data = cowCheck();
-    data->reset();
-    data->newFullPos(*this);
-    setResetFlag(true);
-    data->next();
-    assert(getContainer() == data);
-  }
+  if (!data) return;
+  assert(!data->isStatic());
+  setAd(data);
+  escalateCheck();
+  data = cowCheck();
+  data->reset();
+  data->newFullPos(*this);
+  setResetFlag(true);
+  data->next();
+  assert(getContainer() == data);
 }
 
 MArrayIter::~MArrayIter() {
@@ -621,7 +595,7 @@ bool Iter::minit(TypedValue* v1) {
       hasElems = false;
     }
   } else if (rtv->m_type == KindOfObject)  {
-    if (rtv->m_data.pobj->getCollectionType() != 0) {
+    if (rtv->m_data.pobj->isCollection()) {
       raise_error("Collection elements cannot be taken by reference");
     }
     bool isIterator;
diff --git a/hphp/runtime/base/array/array_iterator.h b/hphp/runtime/base/array/array_iterator.h
index 6ca83fcc3..d0219dae4 100644
--- a/hphp/runtime/base/array/array_iterator.h
+++ b/hphp/runtime/base/array/array_iterator.h
@@ -294,8 +294,7 @@ class FullPos {
   bool prepare();
 
   ArrayData* getArray() const {
-    ArrayData *data = hasVar() ? getData() : getAd();
-    return data;
+    return hasVar() ? getData() : getAd();
   }
 
   bool hasVar() const {
@@ -339,7 +338,10 @@ class FullPos {
   }
 
  protected:
-  ArrayData* getData() const;
+  ArrayData* getData() const {
+    assert(hasVar());
+    return m_var->is(KindOfArray) ? m_var->getArrayData() : nullptr;
+  }
   ArrayData* cowCheck();
   void escalateCheck();
   ArrayData* reregister();
diff --git a/hphp/runtime/base/array/hphp_array.cpp b/hphp/runtime/base/array/hphp_array.cpp
index 29c0b6d77..1e6f8ef0c 100644
--- a/hphp/runtime/base/array/hphp_array.cpp
+++ b/hphp/runtime/base/array/hphp_array.cpp
@@ -1601,7 +1601,7 @@ ArrayData* HphpArray::pop(Variant& value) {
   } else {
     value = uninit_null();
   }
-  // To match PHP-like semantics, the pop operation resets the array's
+  // To conform to PHP behavior, the pop operation resets the array's
   // internal iterator.
   a->m_pos = a->nextElm(elms, ElmIndEmpty);
   return result;
@@ -1613,7 +1613,7 @@ ArrayData* HphpArray::dequeue(Variant& value) {
   if (getCount() > 1) {
     result = a = copyImpl();
   }
-  // To match PHP-like semantics, we invalidate all strong iterators when an
+  // To conform to PHP behavior, we invalidate all strong iterators when an
   // element is removed from the beginning of the array.
   a->freeStrongIterators();
   Elm* elms = a->m_data;
@@ -1628,7 +1628,7 @@ ArrayData* HphpArray::dequeue(Variant& value) {
   } else {
     value = uninit_null();
   }
-  // To match PHP-like semantics, the dequeue operation resets the array's
+  // To conform to PHP behavior, the dequeue operation resets the array's
   // internal iterator
   a->m_pos = ssize_t(a->nextElm(elms, ElmIndEmpty));
   return result;
@@ -1640,7 +1640,7 @@ ArrayData* HphpArray::prepend(CVarRef v, bool copy) {
   if (copy) {
     result = a = copyImpl();
   }
-  // To match PHP-like semantics, we invalidate all strong iterators when an
+  // To conform to PHP behavior, we invalidate all strong iterators when an
   // element is added to the beginning of the array.
   a->freeStrongIterators();
 
@@ -1666,7 +1666,7 @@ ArrayData* HphpArray::prepend(CVarRef v, bool copy) {
 
   // Renumber.
   a->compact(true);
-  // To match PHP-like semantics, the prepend operation resets the array's
+  // To conform to PHP behavior, the prepend operation resets the array's
   // internal iterator
   a->m_pos = ssize_t(a->nextElm(elms, ElmIndEmpty));
   return result;
@@ -1700,19 +1700,22 @@ bool HphpArray::validFullPos(const FullPos &fp) const {
   return (fp.m_pos != ssize_t(ElmIndEmpty));
 }
 
-void HphpArray::getFullPos(FullPos& fp) {
-  assert(fp.getContainer() == (ArrayData*)this);
-  fp.m_pos = m_pos;
-}
-
-bool HphpArray::setFullPos(const FullPos& fp) {
-  assert(fp.getContainer() == (ArrayData*)this);
-  assert(!fp.getResetFlag());
-  if (fp.m_pos != ssize_t(ElmIndEmpty)) {
-    m_pos = fp.m_pos;
-    return true;
+bool HphpArray::advanceFullPos(FullPos& fp) {
+  Elm* elms = m_data;
+  if (fp.getResetFlag()) {
+    fp.setResetFlag(false);
+    fp.m_pos = ElmIndEmpty;
+  } else if (fp.m_pos == ssize_t(ElmIndEmpty)) {
+    return false;
   }
-  return false;
+  fp.m_pos = nextElm(elms, fp.m_pos);
+  if (fp.m_pos == ssize_t(ElmIndEmpty)) {
+    return false;
+  }
+  // To conform to PHP behavior, we need to set the internal
+  // cursor to point to the next element.
+  m_pos = nextElm(elms, fp.m_pos);
+  return true;
 }
 
 CVarRef HphpArray::currentRef() {
diff --git a/hphp/runtime/base/array/hphp_array.h b/hphp/runtime/base/array/hphp_array.h
index d687f6363..b4f524cec 100644
--- a/hphp/runtime/base/array/hphp_array.h
+++ b/hphp/runtime/base/array/hphp_array.h
@@ -180,8 +180,7 @@ public:
 
   // overrides ArrayData
   bool validFullPos(const FullPos &fp) const;
-  void getFullPos(FullPos& fp);
-  bool setFullPos(const FullPos& fp);
+  bool advanceFullPos(FullPos& fp);
   CVarRef currentRef();
   CVarRef endRef();
 
diff --git a/hphp/runtime/vm/name_value_table_wrapper.cpp b/hphp/runtime/vm/name_value_table_wrapper.cpp
index 1030f75c3..d0289c56a 100644
--- a/hphp/runtime/vm/name_value_table_wrapper.cpp
+++ b/hphp/runtime/vm/name_value_table_wrapper.cpp
@@ -282,22 +282,26 @@ bool NameValueTableWrapper::validFullPos(const FullPos & fp) const {
   return (iter.valid());
 }
 
-void NameValueTableWrapper::getFullPos(FullPos &fp) {
-  assert(fp.getContainer() == this);
-  fp.m_pos = m_pos;
-}
-
-bool NameValueTableWrapper::setFullPos(const FullPos& fp) {
-  assert(fp.getContainer() == this);
-  assert(!fp.getResetFlag());
-  if (fp.m_pos != ArrayData::invalid_index) {
-    NameValueTable::Iterator iter(m_tab, fp.m_pos);
-    if (iter.valid()) {
-      m_pos = iter.toInteger();
-      return true;
+bool NameValueTableWrapper::advanceFullPos(FullPos& fp) {
+  bool reset = fp.getResetFlag();
+  NameValueTable::Iterator iter = reset ?
+    NameValueTable::Iterator(m_tab) :
+    NameValueTable::Iterator(m_tab, fp.m_pos);
+  if (reset) {
+    fp.setResetFlag(false);
+  } else {
+    if (!iter.valid()) {
+      return false;
     }
+    iter.next();
   }
-  return false;
+  fp.m_pos = iter.toInteger();
+  if (!iter.valid()) return false;
+  // To conform to PHP behavior, we need to set the internal
+  // cursor to point to the next element.
+  iter.next();
+  m_pos = iter.toInteger();
+  return true;
 }
 
 ArrayData* NameValueTableWrapper::escalateForSort() {
diff --git a/hphp/runtime/vm/name_value_table_wrapper.h b/hphp/runtime/vm/name_value_table_wrapper.h
index acd008e76..d38a9837a 100644
--- a/hphp/runtime/vm/name_value_table_wrapper.h
+++ b/hphp/runtime/vm/name_value_table_wrapper.h
@@ -133,8 +133,7 @@ public: // ArrayData implementation
   virtual Variant value(ssize_t &pos) const;
   virtual Variant each();
   virtual bool validFullPos(const FullPos & fp) const;
-  virtual void getFullPos(FullPos&);
-  virtual bool setFullPos(const FullPos&);
+  virtual bool advanceFullPos(FullPos&);
 
   virtual ArrayData* escalateForSort();
   virtual void ksort(int sort_flags, bool ascending);