diff --git a/README.md b/README.md
index 48c584d..22e8051 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,7 @@ See [stubs](stubs/) directory for signature of all classes and methods of this e
 The `Collection` class implements `ArrayAccess` and `Countable` interface internally, you can treat an instance of `Collection` as an `ArrayObject`.
 
 * The `isset()`, `unset()` keywords can be used on elements of `Collection`.
-* Elements can be accessed via property (string keys only) and bracket expression.
+* Elements can be accessed via property and bracket expression.
 * `empty()`, `count()` can be used on instance of `Collection`.
 * Elements can be traversed via `foreach()` keyword.
 
@@ -48,7 +48,7 @@ $names = Collection::init($employees)
     ->sortedByDescending(function ($value) {
         return $value['age'];
     })
-    ->map(function ($value) {
+    ->mapValues(function ($value) {
         return $value['name'];
     })
     ->toArray();
diff --git a/src/collections_methods.c b/src/collections_methods.c
index d32aa3b..a4db1de 100644
--- a/src/collections_methods.c
+++ b/src/collections_methods.c
@@ -5,6 +5,7 @@
 //
 
 #include <php.h>
+#include <stdint.h>
 
 #include "php_collections.h"
 #include "php_collections_me.h"
@@ -1142,17 +1143,77 @@ PHP_METHOD(Collection, reduceRight)
 
 PHP_METHOD(Collection, remove)
 {
-    
+    zval* key;
+    zval* value = NULL;
+    ZEND_PARSE_PARAMETERS_START(1, 2)
+        Z_PARAM_ZVAL(key)
+        Z_PARAM_OPTIONAL
+        Z_PARAM_ZVAL(value)
+    ZEND_PARSE_PARAMETERS_END();
+    zend_array* current = COLLECTION_FETCH_CURRENT();
+    zval* found;
+    if (Z_TYPE_P(key) == IS_LONG) {
+        if (value == NULL)
+            RETURN_BOOL(zend_hash_index_del(current, Z_LVAL_P(key)) == SUCCESS);
+        found = zend_hash_index_find(current, Z_LVAL_P(key));
+        if (found == NULL || fast_equal_check_function(found, value) == 0)
+            RETURN_FALSE;
+        RETURN_BOOL(zend_hash_index_del(current, Z_LVAL_P(key)) == SUCCESS);
+    }
+    if (Z_TYPE_P(key) == IS_STRING) {
+        if (value == NULL)
+            RETURN_BOOL(zend_hash_del(current, Z_STR_P(key)) == SUCCESS);
+        found = zend_hash_find(current, Z_STR_P(key));
+        if (found == NULL || fast_equal_check_function(found, value) == 0)
+            RETURN_FALSE;
+        RETURN_BOOL(zend_hash_del(current, Z_STR_P(key)) == SUCCESS);
+    }
+    ERR_BAD_KEY_TYPE();
+    RETVAL_FALSE;
 }
 
 PHP_METHOD(Collection, removeAll)
 {
-    
+    zend_fcall_info fci;
+    zend_fcall_info_cache fcc;
+    ZEND_PARSE_PARAMETERS_START(0, 1)
+        Z_PARAM_OPTIONAL
+        Z_PARAM_FUNC(fci, fcc)
+    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(2);
+    ZEND_HASH_FOREACH_BUCKET(current, Bucket* bucket)
+        CALLBACK_KEYVAL_INVOKE(params, bucket);
+        if (zend_is_true(&retval))
+            zend_hash_del_bucket(current, bucket);
+    ZEND_HASH_FOREACH_END();
 }
 
 PHP_METHOD(Collection, retainAll)
 {
-    
+    zend_fcall_info fci;
+    zend_fcall_info_cache fcc;
+    ZEND_PARSE_PARAMETERS_START(0, 1)
+        Z_PARAM_OPTIONAL
+        Z_PARAM_FUNC(fci, fcc)
+    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(2);
+    ZEND_HASH_FOREACH_BUCKET(current, Bucket* bucket)
+        CALLBACK_KEYVAL_INVOKE(params, bucket);
+        if (!zend_is_true(&retval))
+            zend_hash_del_bucket(current, bucket);
+    ZEND_HASH_FOREACH_END();
 }
 
 PHP_METHOD(Collection, reverse)
@@ -1179,12 +1240,13 @@ PHP_METHOD(Collection, set)
         Z_PARAM_ZVAL(value)
     ZEND_PARSE_PARAMETERS_END();
     zend_array* current = COLLECTION_FETCH_CURRENT();
-    SEPARATE_CURRENT_COLLECTION(current);
-    if (Z_TYPE_P(key) == IS_STRING)
+    if (Z_TYPE_P(key) == IS_STRING) {
+        SEPARATE_CURRENT_COLLECTION(current);
         zend_hash_update(current, Z_STR_P(key), value);
-    else if (Z_TYPE_P(key) == IS_LONG)
+    } else if (Z_TYPE_P(key) == IS_LONG) {
+        SEPARATE_CURRENT_COLLECTION(current);
         zend_hash_index_update(current, Z_LVAL_P(key), value);
-    else
+    } else
         ERR_BAD_KEY_TYPE();
 }
 
diff --git a/stubs/Collection.php b/stubs/Collection.php
index 6928203..c400a0d 100644
--- a/stubs/Collection.php
+++ b/stubs/Collection.php
@@ -680,14 +680,16 @@ class Collection implements ArrayAccess, Countable
      *
      * @param int|string $key
      * @param mixed $value[optional]
+     * @return bool
      */
     function remove($key, $value) {}
 
     /**
-     * Removes all elements from this collection that match the given predicate.
+     * Removes all elements from this collection that match the given predicate. If predicate is not
+     * provided, all elements will be removed.
      *
-     * @param callable $predicate ($value, $key) -> bool
-     * @return bool
+     * @param callable $predicate[optional] ($value, $key) -> bool
+     * @return void
      */
     function removeAll($predicate) {}
 
@@ -695,7 +697,7 @@ class Collection implements ArrayAccess, Countable
      * Retains only elements of this collection that match the given predicate.
      *
      * @param callable $predicate ($value, $key) -> bool
-     * @return bool
+     * @return void
      */
     function retainAll($predicate) {}
 
diff --git a/tests/027-get-set.phpt b/tests/027-get-set-remove.phpt
similarity index 68%
rename from tests/027-get-set.phpt
rename to tests/027-get-set-remove.phpt
index 448d0e7..f733133 100644
--- a/tests/027-get-set.phpt
+++ b/tests/027-get-set-remove.phpt
@@ -13,5 +13,9 @@ if ($collection->toArray() != $array)
 if ($collection->get('a') != $array['a'] ||
     $collection->get('f', function ($key) { return $key; }) != 'f')
     echo 'Collection::get() failed.', PHP_EOL;
+if (!$collection->remove('a') || !is_null($collection->get('a')))
+    echo 'Collection::remove() failed.', PHP_EOL;
+if ($collection->remove('c', 'e') || $collection->get('c') != 'd')
+    echo 'Collection::remove() failed.', PHP_EOL;
 ?>
 --EXPECT--
diff --git a/tests/029-remove-retain-all.phpt b/tests/029-remove-retain-all.phpt
new file mode 100644
index 0000000..f10d883
--- /dev/null
+++ b/tests/029-remove-retain-all.phpt
@@ -0,0 +1,21 @@
+--TEST--
+Test Collection::removeAll() and Collection::retainAll().
+--FILE--
+<?php
+$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--