diff --git a/collections.c b/collections.c
index 2c450e6..97f2266 100644
--- a/collections.c
+++ b/collections.c
@@ -14,12 +14,32 @@
 
 #include "php_collections.h"
 
+zend_string* collection_property_name;
+zend_string* pair_first_name;
+zend_string* pair_second_name;
+
+zend_class_entry* collections_collection_ce;
+zend_class_entry* collections_pair_ce;
+
 PHP_MINIT_FUNCTION(collections)
 {
-    INIT_CLASS_ENTRY_EX(collections_collection_ce, "Collection", strlen("Collection"), collection_methods);
-    zend_register_internal_class(&collections_collection_ce);
-    INIT_CLASS_ENTRY_EX(collections_pair_ce, "Pair", strlen("Pair"), pair_methods);
-    zend_register_internal_class(&collections_pair_ce);
+    collection_property_name = zend_string_init("_a", strlen("_a"), 1);
+    pair_first_name = zend_string_init("first", strlen("first"), 1);
+    pair_second_name = zend_string_init("first", strlen("second"), 1);
+    zend_class_entry collection_ce;
+    INIT_CLASS_ENTRY_EX(collection_ce, "Collection", strlen("Collection"), collection_methods);
+    collections_collection_ce = zend_register_internal_class(&collection_ce);
+    zend_class_entry pair_ce;
+    INIT_CLASS_ENTRY_EX(pair_ce, "Pair", strlen("Pair"), pair_methods);
+    collections_pair_ce = zend_register_internal_class(&pair_ce);
+    return SUCCESS;
+}
+
+PHP_MSHUTDOWN_FUNCTION(collections)
+{
+    zend_string_release(collection_property_name);
+    zend_string_release(pair_first_name);
+    zend_string_release(pair_second_name);
     return SUCCESS;
 }
 
@@ -43,7 +63,7 @@ zend_module_entry collections_module_entry = {
     "collections",
     NULL,
     PHP_MINIT(collections),
-    NULL,
+    PHP_MSHUTDOWN(collections),
     PHP_RINIT(collections),
     NULL,
     PHP_MINFO(collections),
diff --git a/collections_fe.c b/collections_fe.c
index 6f6e84e..566ad31 100644
--- a/collections_fe.c
+++ b/collections_fe.c
@@ -3,6 +3,7 @@
 //
 // @Author CismonX
 //
+
 #include <php.h>
 
 #include "php_collections.h"
diff --git a/collections_methods.c b/collections_methods.c
new file mode 100644
index 0000000..63f2a2e
--- /dev/null
+++ b/collections_methods.c
@@ -0,0 +1,606 @@
+//
+// ext-collections/collections_methods.c
+//
+// @Author CismonX
+//
+
+#include <php.h>
+
+#include "php_collections.h"
+#include "php_collections_fe.h"
+
+#define NEW_COLLECTION_OBJ(name) \
+    zend_object* (name) = (zend_object*)ecalloc(1, sizeof(zend_object) + \
+    zend_object_properties_size(collections_collection_ce)); \
+    zend_object_std_init(name, collections_collection_ce); \
+    object_properties_init(name, collections_collection_ce); \
+    obj->handlers = &std_object_handlers;
+
+#define IS_COLLECTION(zval) \
+    Z_TYPE_P(elements) == IS_OBJECT && Z_OBJCE_P(elements) == collections_collection_ce
+
+#define COLLECTION_UPDATE(obj, value) \
+    zend_update_property_ex(zend_get_executed_scope(), obj, collection_property_name, value)
+#define COLLECTION_UPDATE_EX(value) COLLECTION_UPDATE(getThis(), value)
+#define COLLECTION_FETCH(obj) \
+    zend_read_property_ex(zend_get_executed_scope(), obj, collection_property_name, 1, &rv)
+#define COLLECTION_FETCH_EX() COLLECTION_FETCH(getThis())
+
+#define PHP_COLLECTIONS_ERROR(type, msg) php_error_docref(NULL, type, msg)
+#define ERR_BAD_ARGUMENT_TYPE() PHP_COLLECTIONS_ERROR(E_WARNING, "Bad argument type")
+
+PHP_METHOD(Collection, __construct)
+{
+    
+}
+
+PHP_METHOD(Collection, addAll)
+{
+    
+}
+
+PHP_METHOD(Collection, all)
+{
+    
+}
+
+PHP_METHOD(Collection, any)
+{
+    
+}
+
+PHP_METHOD(Collection, associate)
+{
+    
+}
+
+PHP_METHOD(Collection, associateTo)
+{
+    
+}
+
+PHP_METHOD(Collection, associateBy)
+{
+    
+}
+
+PHP_METHOD(Collection, associateByTo)
+{
+    
+}
+
+PHP_METHOD(Collection, average)
+{
+    
+}
+
+PHP_METHOD(Collection, containsAll)
+{
+    
+}
+
+PHP_METHOD(Collection, containsKey)
+{
+    
+}
+
+PHP_METHOD(Collection, containsValue)
+{
+    
+}
+
+PHP_METHOD(Collection, copyOf)
+{
+    
+}
+
+PHP_METHOD(Collection, copyOfRange)
+{
+    
+}
+
+PHP_METHOD(Collection, count)
+{
+    
+}
+
+PHP_METHOD(Collection, distinct)
+{
+    
+}
+
+PHP_METHOD(Collection, distinctBy)
+{
+    
+}
+
+PHP_METHOD(Collection, drop)
+{
+    
+}
+
+PHP_METHOD(Collection, dropLast)
+{
+    
+}
+
+PHP_METHOD(Collection, dropLastWhile)
+{
+    
+}
+
+PHP_METHOD(Collection, dropWhile)
+{
+    
+}
+
+PHP_METHOD(Collection, fill)
+{
+    
+}
+
+PHP_METHOD(Collection, filter)
+{
+    
+}
+
+PHP_METHOD(Collection, filterNot)
+{
+    
+}
+
+PHP_METHOD(Collection, filterNotTo)
+{
+    
+}
+
+PHP_METHOD(Collection, filterTo)
+{
+    
+}
+
+PHP_METHOD(Collection, find)
+{
+    
+}
+
+PHP_METHOD(Collection, findLast)
+{
+    
+}
+
+PHP_METHOD(Collection, first)
+{
+    
+}
+
+PHP_METHOD(Collection, flatMap)
+{
+    
+}
+
+PHP_METHOD(Collection, flatMapTo)
+{
+    
+}
+
+PHP_METHOD(Collection, flatten)
+{
+    
+}
+
+PHP_METHOD(Collection, fold)
+{
+    
+}
+
+PHP_METHOD(Collection, foldRight)
+{
+    
+}
+
+PHP_METHOD(Collection, forEach)
+{
+    
+}
+
+PHP_METHOD(Collection, get)
+{
+    
+}
+
+PHP_METHOD(Collection, groupBy)
+{
+    
+}
+
+PHP_METHOD(Collection, groupByTo)
+{
+    
+}
+
+PHP_METHOD(Collection, indexOf)
+{
+    
+}
+
+PHP_METHOD(Collection, indexOfFirst)
+{
+    
+}
+
+PHP_METHOD(Collection, indexOfLast)
+{
+    
+}
+
+PHP_METHOD(Collection, init)
+{
+    zval* elements = NULL;
+    ZEND_PARSE_PARAMETERS_START(0, 1)
+        Z_PARAM_OPTIONAL
+        Z_PARAM_ZVAL(elements)
+    ZEND_PARSE_PARAMETERS_END();
+    NEW_COLLECTION_OBJ(obj);
+    zval retval;
+    ZVAL_OBJ(&retval, obj);
+    if (elements) {
+        if (IS_COLLECTION(elements)) {
+            zval rv;
+            elements = COLLECTION_FETCH(elements);
+        } else if (UNEXPECTED(Z_TYPE_P(elements) != IS_ARRAY)) {
+            ERR_BAD_ARGUMENT_TYPE();
+            RETVAL_NULL();
+        }
+        COLLECTION_UPDATE(&retval, elements);
+    } else {
+        zval collection;
+        ZVAL_NEW_ARR(&collection);
+        zend_hash_init(Z_ARRVAL(collection), 0, NULL, ZVAL_PTR_DTOR, 0);
+        COLLECTION_UPDATE(&retval, &collection);
+        zval_ptr_dtor(&collection);
+    }
+    ZVAL_COPY_VALUE(return_value, &retval);
+}
+
+PHP_METHOD(Collection, intersect)
+{
+    
+}
+
+PHP_METHOD(Collection, isEmpty)
+{
+    
+}
+
+PHP_METHOD(Collection, isNotEmpty)
+{
+    
+}
+
+PHP_METHOD(Collection, keys)
+{
+    
+}
+
+PHP_METHOD(Collection, last)
+{
+    
+}
+
+PHP_METHOD(Collection, lastIndexOf)
+{
+    
+}
+
+PHP_METHOD(Collection, map)
+{
+    
+}
+
+PHP_METHOD(Collection, mapKeys)
+{
+    
+}
+
+PHP_METHOD(Collection, mapKeysTo)
+{
+    
+}
+
+PHP_METHOD(Collection, mapTo)
+{
+    
+}
+
+PHP_METHOD(Collection, mapValues)
+{
+    
+}
+
+PHP_METHOD(Collection, mapValuesTo)
+{
+    
+}
+
+PHP_METHOD(Collection, max)
+{
+    
+}
+
+PHP_METHOD(Collection, maxBy)
+{
+    
+}
+
+PHP_METHOD(Collection, maxWith)
+{
+    
+}
+
+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, offsetUnset)
+{
+    
+}
+
+PHP_METHOD(Collection, offsetSet)
+{
+    
+}
+
+PHP_METHOD(Collection, offsetGet)
+{
+    
+}
+
+PHP_METHOD(Collection, offsetExists)
+{
+    
+}
+
+PHP_METHOD(Collection, onEach)
+{
+    
+}
+
+PHP_METHOD(Collection, orEmpty)
+{
+    
+}
+
+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, retainAll)
+{
+    
+}
+
+PHP_METHOD(Collection, reverse)
+{
+    
+}
+
+PHP_METHOD(Collection, reversed)
+{
+    
+}
+
+PHP_METHOD(Collection, shuffle)
+{
+    
+}
+
+PHP_METHOD(Collection, single)
+{
+    
+}
+
+PHP_METHOD(Collection, slice)
+{
+    
+}
+
+PHP_METHOD(Collection, sliceRange)
+{
+    
+}
+
+PHP_METHOD(Collection, sort)
+{
+    
+}
+
+PHP_METHOD(Collection, sortBy)
+{
+    
+}
+
+PHP_METHOD(Collection, sortByDescending)
+{
+    
+}
+
+PHP_METHOD(Collection, sortDescending)
+{
+    
+}
+
+PHP_METHOD(Collection, sortWith)
+{
+    
+}
+
+PHP_METHOD(Collection, sorted)
+{
+    
+}
+
+PHP_METHOD(Collection, sortedBy)
+{
+    
+}
+
+PHP_METHOD(Collection, sortedByDescending)
+{
+    
+}
+
+PHP_METHOD(Collection, sortedDescending)
+{
+    
+}
+
+PHP_METHOD(Collection, sortedWith)
+{
+    
+}
+
+PHP_METHOD(Collection, take)
+{
+    
+}
+
+PHP_METHOD(Collection, takeLast)
+{
+    
+}
+
+PHP_METHOD(Collection, takeLastWhile)
+{
+    
+}
+
+PHP_METHOD(Collection, takeWhile)
+{
+    
+}
+
+PHP_METHOD(Collection, toArray)
+{
+    zval rv;
+    zval* data = COLLECTION_FETCH_EX();
+    RETVAL_ZVAL(data, 1, 0);
+}
+
+PHP_METHOD(Collection, toCollection)
+{
+    
+}
+
+PHP_METHOD(Collection, toPairs)
+{
+    
+}
+
+PHP_METHOD(Collection, union)
+{
+    
+}
+
+PHP_METHOD(Collection, values)
+{
+    
+}
+
+PHP_METHOD(Pair, __construct)
+{
+    
+}
\ No newline at end of file
diff --git a/config.m4 b/config.m4
index ddaa2b1..9a8d656 100644
--- a/config.m4
+++ b/config.m4
@@ -6,9 +6,9 @@ PHP_ARG_ENABLE(collections, for debug support,
 
 if test "$PHP_COLLECTIONS" != "no"; then
   if test "$PHP_COLLECTIONS_DEBUG" != "no"; then
-    CFLAGS="-O2"
-  else
     CFLAGS="-g -O0"
+  else
+    CFLAGS="-O2"
   fi
   COLLECTIONS_SRC="collections.c collections_fe.c collections_methods.c"
   PHP_NEW_EXTENSION(collections, $COLLECTIONS_SRC, $ext_shared)
diff --git a/php_collections.h b/php_collections.h
index 5768651..916c36c 100644
--- a/php_collections.h
+++ b/php_collections.h
@@ -10,12 +10,6 @@
 extern zend_module_entry collections_module_entry;
 #define phpext_collections_ptr &collections_module_entry
 
-extern zend_class_entry collections_collection_ce;
-extern zend_class_entry collections_pair_ce;
-
-extern const zend_function_entry collection_methods[];
-extern const zend_function_entry pair_methods[];
-
 #define PHP_COLLECTIONS_VERSION "0.1.0"
 
 #ifdef PHP_WIN32
@@ -26,6 +20,16 @@ extern const zend_function_entry pair_methods[];
 #define PHP_COLLECTIONS_API
 #endif
 
+extern zend_string* collection_property_name;
+extern zend_string* pair_first_name;
+extern zend_string* pair_second_name;
+
+extern PHP_COLLECTIONS_API zend_class_entry* collections_collection_ce;
+extern PHP_COLLECTIONS_API zend_class_entry* collections_pair_ce;
+
+extern const zend_function_entry collection_methods[];
+extern const zend_function_entry pair_methods[];
+
 #ifdef ZTS
 #include "TSRM.h"
 #endif
diff --git a/php_collections_fe.h b/php_collections_fe.h
index ba2b185..b5e1fa0 100644
--- a/php_collections_fe.h
+++ b/php_collections_fe.h
@@ -7,8 +7,6 @@
 #ifndef PHP_COLLECTIONS_FE_H
 #define PHP_COLLECTIONS_FE_H
 
-#include <php.h>
-
 PHP_METHOD(Collection, __construct);
 PHP_METHOD(Collection, addAll);
 PHP_METHOD(Collection, all);
diff --git a/stubs/Collection.php b/stubs/Collection.php
index 8832f05..10d1bcf 100644
--- a/stubs/Collection.php
+++ b/stubs/Collection.php
@@ -418,7 +418,7 @@ class Collection implements ArrayAccess, Countable
      * Returns a collection containing the results of applying the given transform function
      * to each element in the original collection.
      *
-     * @param callable $transform ($value, $key) -> $new_value
+     * @param callable $transform ($value, $key) -> Pair
      * @return Collection
      */
     function map($transform) {}
@@ -447,7 +447,7 @@ class Collection implements ArrayAccess, Countable
      * results to the given destination.
      *
      * @param Collection $destination
-     * @param callable $transform ($value, $key) -> $new_value
+     * @param callable $transform ($value, $key) -> Pair
      * @return Collection
      */
     function mapTo($destination, $transform) {}
diff --git a/stubs/Pair.php b/stubs/Pair.php
index 7ffb5ab..e67d048 100644
--- a/stubs/Pair.php
+++ b/stubs/Pair.php
@@ -5,15 +5,25 @@
  */
 class Pair
 {
+    /**
+     * First value of the pair.
+     *
+     * @var mixed $first
+     */
     public $first;
 
+    /**
+     * Second value of the pair.
+     *
+     * @var mixed $second
+     */
     public $second;
 
     /**
      * Constructor.
      *
-     * @param $first
-     * @param $second
+     * @param mixed $first
+     * @param mixed $second
      */
     function __construct($first, $second) {}
 }
\ No newline at end of file