diff --git a/src/collections_me.c b/src/collections_me.c
index a0dc675..5dd8abd 100644
--- a/src/collections_me.c
+++ b/src/collections_me.c
@@ -178,25 +178,18 @@ const zend_function_entry collection_methods[] = {
     PHP_ME(Collection, minBy, selector_flags_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, minWith, comparator_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, minus, elements_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, minusAssign, elements_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, minusKeys, keys_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, minusKeysAssign, keys_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, minusValues, elements_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, minusValuesAssign, elements_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, none, predicate_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, onEach, action_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, packed, NULL, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, partition, predicate_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, plus, elements_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, plusAssign, elements_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, plusValues, elements_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, plusValuesAssign, elements_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, putAll, elements_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, reduce, operation_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, reduceRight, operation_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, remove, key_value_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, removeAll, predicate_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, retainAll, predicate_arginfo, ZEND_ACC_PUBLIC)
+    PHP_ME(Collection, removeAll, other_arginfo, ZEND_ACC_PUBLIC)
+    PHP_ME(Collection, removeWhile, predicate_arginfo, ZEND_ACC_PUBLIC)
+    PHP_ME(Collection, retainAll, other_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, reverse, NULL, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, reversed, NULL, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, shuffle, NULL, ZEND_ACC_PUBLIC)
diff --git a/src/collections_methods.c b/src/collections_methods.c
index a54203c..3af1107 100644
--- a/src/collections_methods.c
+++ b/src/collections_methods.c
@@ -1950,31 +1950,6 @@ PHP_METHOD(Collection, minus)
     
 }
 
-PHP_METHOD(Collection, minusAssign)
-{
-    
-}
-
-PHP_METHOD(Collection, minusKeys)
-{
-    
-}
-
-PHP_METHOD(Collection, minusKeysAssign)
-{
-    
-}
-
-PHP_METHOD(Collection, minusValues)
-{
-    
-}
-
-PHP_METHOD(Collection, minusValuesAssign)
-{
-    
-}
-
 PHP_METHOD(Collection, none)
 {
     zend_fcall_info fci;
@@ -2056,21 +2031,6 @@ PHP_METHOD(Collection, plus)
     
 }
 
-PHP_METHOD(Collection, plusAssign)
-{
-    
-}
-
-PHP_METHOD(Collection, plusValues)
-{
-    
-}
-
-PHP_METHOD(Collection, plusValuesAssign)
-{
-    
-}
-
 PHP_METHOD(Collection, putAll)
 {
     zval* elements;
@@ -2207,6 +2167,11 @@ PHP_METHOD(Collection, remove)
 }
 
 PHP_METHOD(Collection, removeAll)
+{
+
+}
+
+PHP_METHOD(Collection, removeWhile)
 {
     zend_fcall_info fci;
     zend_fcall_info_cache fcc;
@@ -2216,10 +2181,6 @@ PHP_METHOD(Collection, removeAll)
     ZEND_PARSE_PARAMETERS_END();
     zend_array* current = COLLECTION_FETCH_CURRENT();
     SEPARATE_CURRENT_COLLECTION(current);
-    if (EX_NUM_ARGS() == 0) {
-        zend_hash_clean(current);
-        return;
-    }
     INIT_FCI(&fci, 2);
     ZEND_HASH_FOREACH_BUCKET(current, Bucket* bucket)
         CALLBACK_KEYVAL_INVOKE(params, bucket);
@@ -2232,21 +2193,7 @@ PHP_METHOD(Collection, removeAll)
 
 PHP_METHOD(Collection, retainAll)
 {
-    zend_fcall_info fci;
-    zend_fcall_info_cache fcc;
-    ZEND_PARSE_PARAMETERS_START(1, 1)
-        Z_PARAM_FUNC(fci, fcc)
-    ZEND_PARSE_PARAMETERS_END();
-    zend_array* current = COLLECTION_FETCH_CURRENT();
-    SEPARATE_CURRENT_COLLECTION(current);
-    INIT_FCI(&fci, 2);
-    ZEND_HASH_FOREACH_BUCKET(current, Bucket* bucket)
-        CALLBACK_KEYVAL_INVOKE(params, bucket);
-        if (!zend_is_true(&retval)) {
-            zend_hash_del_bucket(current, bucket);
-        }
-        zval_ptr_dtor(&retval);
-    ZEND_HASH_FOREACH_END();
+    
 }
 
 PHP_METHOD(Collection, reverse)
diff --git a/src/php_collections_me.h b/src/php_collections_me.h
index 134738b..efa9840 100644
--- a/src/php_collections_me.h
+++ b/src/php_collections_me.h
@@ -66,24 +66,17 @@ PHP_METHOD(Collection, min);
 PHP_METHOD(Collection, minBy);
 PHP_METHOD(Collection, minWith);
 PHP_METHOD(Collection, minus);
-PHP_METHOD(Collection, minusAssign);
-PHP_METHOD(Collection, minusKeys);
-PHP_METHOD(Collection, minusKeysAssign);
-PHP_METHOD(Collection, minusValues);
-PHP_METHOD(Collection, minusValuesAssign);
 PHP_METHOD(Collection, none);
 PHP_METHOD(Collection, onEach);
 PHP_METHOD(Collection, packed);
 PHP_METHOD(Collection, partition);
 PHP_METHOD(Collection, plus);
-PHP_METHOD(Collection, plusAssign);
-PHP_METHOD(Collection, plusValues);
-PHP_METHOD(Collection, plusValuesAssign);
 PHP_METHOD(Collection, putAll);
 PHP_METHOD(Collection, reduce);
 PHP_METHOD(Collection, reduceRight);
 PHP_METHOD(Collection, remove);
 PHP_METHOD(Collection, removeAll);
+PHP_METHOD(Collection, removeWhile);
 PHP_METHOD(Collection, retainAll);
 PHP_METHOD(Collection, reverse);
 PHP_METHOD(Collection, reversed);
diff --git a/stubs/Collection.php b/stubs/Collection.php
index ffc248e..72f4da1 100644
--- a/stubs/Collection.php
+++ b/stubs/Collection.php
@@ -539,49 +539,6 @@ class Collection implements ArrayAccess, Countable
      */
     function minus($elements) {}
 
-    /**
-     * Removes all key-value pairs contained in the given collection from this collection.
-     *
-     * @param array|Collection $elements
-     * @return void
-     */
-    function minusAssign($elements) {}
-
-    /**
-     * Returns a collection containing all entries of the original collection except those entries
-     * the keys of which are contained in the given keys collection.
-     *
-     * @param array|Collection $keys
-     * @return Collection
-     */
-    function minusKeys($keys) {}
-
-    /**
-     * Removes all entries the keys of which are contained in the given keys collection from this
-     * collection.
-     *
-     * @param array|Collection $keys
-     * @return void
-     */
-    function minusKeysAssign($keys) {}
-
-    /**
-     * Returns a list containing all elements of the original collection except the elements contained
-     * in the given elements collection.
-     *
-     * @param array|Collection $elements
-     * @return Collection
-     */
-    function minusValues($elements) {}
-
-    /**
-     * Removes all elements contained in the given elements collection from this collection.
-     *
-     * @param array|Collection $elements
-     * @return void
-     */
-    function minusValuesAssign($elements) {}
-
     /**
      * Returns true if no elements match the given predicate.
      *
@@ -648,39 +605,13 @@ class Collection implements ArrayAccess, Countable
     function partition($predicate) {}
 
     /**
-     * Creates a new collection by replacing or adding entries to this collection from a given
-     * collection of key-value pairs.
+     * Creates a new collection by replacing or elements to this collection from a given collection.
      *
      * @param array|Collection $elements
      * @return Collection
      */
     function plus($elements) {}
 
-    /**
-     * Appends or replaces all pairs from the given collection of pairs in this collection.
-     *
-     * @param array|Collection $elements
-     * @return void
-     */
-    function plusAssign($elements) {}
-
-    /**
-     * Returns a collection containing all elements of the original collection and then all elements
-     * of the given elements collection.
-     *
-     * @param array|Collection $elements
-     * @return Collection
-     */
-    function plusValues($elements) {}
-
-    /**
-     * Adds all elements of the given elements collection to this collection.
-     *
-     * @param array|Collection $elements
-     * @return void
-     */
-    function plusValuesAssign($elements) {}
-
     /**
      * Puts all the elements of the given collection into this collection.
      *
@@ -717,21 +648,28 @@ class Collection implements ArrayAccess, Countable
     function remove($key, $value) {}
 
     /**
-     * Removes all elements from this collection that match the given predicate. If predicate is not
-     * provided, all elements will be removed.
+     * Removes elements of this collection whose values exists in the given collection.
      *
-     * @param callable $predicate[optional] ($value, $key) -> bool
+     * @param array|Collection $elements[optional]
      * @return void
      */
-    function removeAll($predicate) {}
+    function removeAll($elements) {}
 
     /**
-     * Retains only elements of this collection that match the given predicate.
+     * Removes all elements from this collection that match the given predicate.
      *
      * @param callable $predicate ($value, $key) -> bool
      * @return void
      */
-    function retainAll($predicate) {}
+    function removeWhile($predicate) {}
+
+    /**
+     * Retains elements of this collection whose values exists in the given collection.
+     *
+     * @param array|Collection $elements
+     * @return void
+     */
+    function retainAll($elements) {}
 
     /**
      * Reverses elements in the collection in-place.
diff --git a/tests/029-remove-retain-all.phpt b/tests/029-remove-retain-all.phpt
deleted file mode 100644
index 64e5566..0000000
--- a/tests/029-remove-retain-all.phpt
+++ /dev/null
@@ -1,24 +0,0 @@
---TEST--
-Test Collection::removeAll() and Collection::retainAll().
---FILE--
-<?php
-$array = ['a' => 4, 'b' => 1, 'c' => 9, 'd' => -2, 'e' => 0];
-$pred_is_odd = function ($value) {
-    return $value % 2;
-};
-$collection = Collection::init($array);
-$collection->removeAll($pred_is_odd);
-if ($collection->toArray() != ['a' => 4, 'd' => -2, 'e' => 0]) {
-    echo 'Collection::removeAll() failed.', PHP_EOL;
-}
-$collection->removeAll();
-if ($collection->toArray() != []) {
-    echo 'Collection::removeAll() failed.', PHP_EOL;
-}
-$collection = Collection::init($array);
-$collection->retainAll($pred_is_odd);
-if ($collection->toArray() != ['b' => 1, 'c' => 9]) {
-    echo 'Collection::retainAll() failed.', PHP_EOL;
-}
-?>
---EXPECT--
diff --git a/tests/029-remove-while.phpt b/tests/029-remove-while.phpt
new file mode 100644
index 0000000..5593776
--- /dev/null
+++ b/tests/029-remove-while.phpt
@@ -0,0 +1,15 @@
+--TEST--
+Test Collection::removeWhile().
+--FILE--
+<?php
+$array = ['a' => 4, 'b' => 1, 'c' => 9, 'd' => -2, 'e' => 0];
+$pred_is_odd = function ($value) {
+    return $value % 2;
+};
+$collection = Collection::init($array);
+$collection->removeWhile($pred_is_odd);
+if ($collection->toArray() != ['a' => 4, 'd' => -2, 'e' => 0]) {
+    echo 'Collection::removeWhile() failed.', PHP_EOL;
+}
+?>
+--EXPECT--