diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..5ec68ea
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/vendor/
+composer.lock
+coverage.html
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..43f7b46
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,15 @@
+tester = vendor/bin/tester
+tests_dir = tests/
+coverage_name = $(tests_dir)coverage.html
+php_ini = $(tests_dir)php-unix.ini
+php_bin = php
+
+.PHONY: test coverage clean
+test:
+		@$(tester) -p $(php_bin) -c $(php_ini) $(tests_dir)
+
+coverage:
+		@$(tester) -p $(php_bin) -c $(php_ini) --coverage $(coverage_name) --coverage-src src/ $(tests_dir)
+
+clean:
+		@rm -f $(coverage_name)
diff --git a/composer.json b/composer.json
new file mode 100644
index 0000000..97cd6e1
--- /dev/null
+++ b/composer.json
@@ -0,0 +1,21 @@
+{
+	"name": "czproject/arrays",
+	"type": "library",
+	"description": "Array tools library.",
+	"license": "BSD-3-Clause",
+	"authors": [
+		{
+			"name": "Jan Pecha",
+			"homepage": "https://www.janpecha.cz/"
+		}
+	],
+	"require": {
+		"php": ">=5.4.0"
+	},
+	"autoload": {
+		"classmap": ["src/"]
+	},
+	"require-dev": {
+		"nette/tester": "^1.7"
+	}
+}
diff --git a/license.md b/license.md
new file mode 100644
index 0000000..4c52135
--- /dev/null
+++ b/license.md
@@ -0,0 +1,26 @@
+New BSD License
+---------------
+
+Copyright © 2016 Jan Pecha (https://www.janpecha.cz/) All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+* Redistributions in binary form must reproduce the above copyright notice, this
+  list of conditions and the following disclaimer in the documentation and/or
+  other materials provided with the distribution.
+* Neither the name of “CzProject“ nor the names of its contributors may be used to
+  endorse or promote products derived from this software without specific prior
+  written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/readme.md b/readme.md
new file mode 100644
index 0000000..fad9d7d
--- /dev/null
+++ b/readme.md
@@ -0,0 +1,148 @@
+
+# CzProject\Arrays
+
+Array tools library.
+
+## Usage
+
+
+``` php
+<?php
+
+use CzProject\Arrays;
+
+```
+
+### `flatten()`
+
+``` php
+<?php
+
+$data = Arrays::flatten(array(
+	'value 1',
+	'values' => array(
+		'value 2-1',
+		'value 2-2',
+		'value 2-3',
+	),
+	'value 3',
+));
+
+/* Returns:
+[
+	'value 1',
+	'value 2-1',
+	'value 2-2',
+	'value 2-3',
+	'value 3',
+]
+*/
+```
+
+
+### `fetchPairs()`
+
+``` php
+<?php
+
+$rows = array(
+	array(
+		'id' => 1,
+		'name' => 'Row #1',
+	),
+
+	array(
+		'id' => 2,
+		'name' => 'Row #2',
+	),
+
+	array(
+		'id' => 3,
+		'name' => 'Row #3',
+	),
+);
+
+$data = Arrays::fetchPairs($rows, 'id', 'name');
+
+/* Returns:
+[
+	1 => 'Row #1',
+	2 => 'Row #2',
+	3 => 'Row #3',
+]
+*/
+```
+
+
+### `merge()`
+
+``` php
+<?php
+
+$defaultConfig = array(
+	'parameters' => array(
+		'database' => array(
+			'host' => 'localhost',
+			'database' => 'lorem_ipsum',
+			'driver' => 'mysql',
+		),
+	),
+
+	'messages' => array(
+		'success' => 'Success!',
+		'error' => 'Error!',
+	),
+);
+
+$config = array(
+	'parameters' => array(
+		'database' => array(
+			'user' => 'user123',
+			'password' => 'password123',
+		),
+	),
+
+	'messages' => array(
+		'error' => 'Fatal Error!',
+	),
+);
+
+$data = Arrays::merge($config, $defaultConfig);
+
+/* Returns:
+[
+	parameters => [
+		database => [
+			host => 'localhost',
+			database => 'lorem_ipsum',
+			driver => 'mysql',
+			user => 'user123',
+			password => 'password123',
+		]
+	],
+
+	messages => [
+		success => 'Success!',
+		error => 'Fatal Error!',
+	]
+]
+*/
+```
+
+
+Installation
+------------
+
+[Download a latest package](https://github.com/czproject/arrays/releases) or use [Composer](http://getcomposer.org/):
+
+```
+composer require [--dev] czproject/arrays
+```
+
+`CzProject\Arrays` requires PHP 5.4.0 or later.
+
+
+------------------------------
+
+License: [New BSD License](license.md)
+<br>Author: Jan Pecha, https://www.janpecha.cz/
diff --git a/src/Arrays.php b/src/Arrays.php
new file mode 100644
index 0000000..251c823
--- /dev/null
+++ b/src/Arrays.php
@@ -0,0 +1,109 @@
+<?php
+
+	namespace CzProject;
+
+
+	class Arrays
+	{
+		/**
+		 * @param  array|\Traversable
+		 * @return array
+		 */
+		public static function flatten($arr)
+		{
+			$res = array();
+
+			static::recursiveWalk($arr, function ($val, $key) use (&$res) {
+				if (is_scalar($val)) {
+					$res[] = $val;
+				}
+			});
+
+			return $res;
+		}
+
+
+		/**
+		 * @param  array|\Traversable
+		 * @return void
+		 */
+		public static function recursiveWalk($arr, $callback)
+		{
+			foreach ($arr as $key => $value) {
+				if (is_array($value) || $value instanceof \Traversable) {
+					static::recursiveWalk($value, $callback);
+
+				} else {
+					call_user_func_array($callback, array($value, $key));
+					// $callback($value, $key);
+				}
+			}
+		}
+
+
+		/**
+		 * @param  array|object[]
+		 * @param  string|callback
+		 * @param  string|callback
+		 * @return array
+		 */
+		public static function fetchPairs($data, $key, $value)
+		{
+			$list = array();
+
+			foreach ($data as $row) {
+				$itemKey = NULL;
+				$itemLabel = NULL;
+
+				if (is_callable($key)) {
+					$itemKey = call_user_func_array($key, array($row));
+
+				} else {
+					$itemKey = is_array($row) ? $row[$key] : $row->{$key};
+				}
+
+				if (is_callable($value)) {
+					$itemLabel = call_user_func_array($value, array($row));
+
+				} else {
+					$itemLabel = is_array($row) ? $row[$value] : $row->{$value};
+				}
+
+				$list[$itemKey] = $itemLabel;
+			}
+
+			return $list;
+		}
+
+
+			/**
+			 * Merges arrays. Left has higher priority than right one.
+			 * @param  array|NULL
+			 * @param  array|NULL
+			 * @return array|string
+			 * @see    https://github.com/nette/di/blob/master/src/DI/Config/Helpers.php
+			 */
+			public static function merge($left, $right)
+			{
+				if (is_array($left) && is_array($right)) {
+					foreach ($left as $key => $val) {
+						if (is_int($key)) {
+							$right[] = $val;
+
+						} else {
+							if (isset($right[$key])) {
+								$val = static::merge($val, $right[$key]);
+							}
+							$right[$key] = $val;
+						}
+					}
+					return $right;
+
+				} elseif ($left === NULL && is_array($right)) {
+					return $right;
+
+				} else {
+					return $left;
+				}
+			}
+	}
diff --git a/tests/Arrays/fetchPairs.phpt b/tests/Arrays/fetchPairs.phpt
new file mode 100644
index 0000000..fcf00b1
--- /dev/null
+++ b/tests/Arrays/fetchPairs.phpt
@@ -0,0 +1,71 @@
+<?php
+
+use CzProject\Arrays;
+use Tester\Assert;
+
+require __DIR__ . '/../bootstrap.php';
+
+
+test(function () {
+
+	$rows = array(
+		array(
+			'id' => 1,
+			'name' => 'Row #1',
+		),
+
+		array(
+			'id' => 2,
+			'name' => 'Row #2',
+		),
+
+		array(
+			'id' => 3,
+			'name' => 'Row #3',
+		),
+	);
+
+	$data = Arrays::fetchPairs($rows, 'id', 'name');
+
+	Assert::same(array(
+		1 => 'Row #1',
+		2 => 'Row #2',
+		3 => 'Row #3',
+	), $data);
+
+});
+
+
+test(function () {
+
+	$rows = array(
+		array(
+			'id' => 1,
+			'name' => 'Row #1',
+		),
+
+		array(
+			'id' => 2,
+			'name' => 'Row #2',
+		),
+
+		array(
+			'id' => 3,
+			'name' => 'Row #3',
+		),
+	);
+
+	$data = Arrays::fetchPairs($rows, function ($row) {
+		return $row['id'] + 10;
+
+	}, function ($row) {
+		return strtoupper($row['name']);
+	});
+
+	Assert::same(array(
+		11 => 'ROW #1',
+		12 => 'ROW #2',
+		13 => 'ROW #3',
+	), $data);
+
+});
diff --git a/tests/Arrays/flatten.phpt b/tests/Arrays/flatten.phpt
new file mode 100644
index 0000000..4828ea4
--- /dev/null
+++ b/tests/Arrays/flatten.phpt
@@ -0,0 +1,27 @@
+<?php
+
+use CzProject\Arrays;
+use Tester\Assert;
+
+require __DIR__ . '/../bootstrap.php';
+
+
+test(function () {
+
+	Assert::same(array(
+		'value 1',
+		'value 2-1',
+		'value 2-2',
+		'value 2-3',
+		'value 3',
+	), Arrays::flatten(array(
+		'value 1',
+		'values' => array(
+			'value 2-1',
+			'value 2-2',
+			'value 2-3',
+		),
+		'value 3',
+	)));
+
+});
diff --git a/tests/Arrays/merge.phpt b/tests/Arrays/merge.phpt
new file mode 100644
index 0000000..acb3c57
--- /dev/null
+++ b/tests/Arrays/merge.phpt
@@ -0,0 +1,116 @@
+<?php
+
+use CzProject\Arrays;
+use Tester\Assert;
+
+require __DIR__ . '/../bootstrap.php';
+
+
+test(function () {
+
+	$defaultConfig = array(
+		'parameters' => array(
+			'database' => array(
+				'host' => 'localhost',
+				'database' => 'lorem_ipsum',
+				'driver' => 'mysql',
+			),
+		),
+
+		'messages' => array(
+			'success' => 'Success!',
+			'error' => 'Error!',
+		),
+	);
+
+	$config = array(
+		'parameters' => array(
+			'database' => array(
+				'user' => 'user123',
+				'password' => 'password123',
+			),
+		),
+
+		'messages' => array(
+			'error' => 'Fatal Error!',
+		),
+	);
+
+	$data = Arrays::merge($config, $defaultConfig);
+
+	Assert::same(array(
+		'parameters' => array(
+			'database' => array(
+				'host' => 'localhost',
+				'database' => 'lorem_ipsum',
+				'driver' => 'mysql',
+				'user' => 'user123',
+				'password' => 'password123',
+			),
+		),
+
+		'messages' => array(
+			'success' => 'Success!',
+			'error' => 'Fatal Error!',
+		)
+	), $data);
+
+});
+
+
+test(function () {
+
+	$data = array(
+		'parameters' => array(
+			'host' => 'localhost',
+		),
+	);
+
+	Assert::same($data, Arrays::merge(NULL, $data));
+
+});
+
+
+test(function () {
+
+	$data = array(
+		'parameters' => array(
+			'host' => 'localhost',
+		),
+	);
+
+	Assert::same($data, Arrays::merge($data, NULL));
+
+});
+
+
+test(function () {
+
+	$default = array(
+		'parameters' => array(
+			'host' => 'localhost',
+		),
+		'ignore' => array(
+			'.git*',
+			'/vendor/',
+		),
+	);
+
+	$config = array(
+		'ignore' => array(
+			'*.txt',
+		),
+	);
+
+	Assert::same(array(
+		'parameters' => array(
+			'host' => 'localhost',
+		),
+		'ignore' => array(
+			'.git*',
+			'/vendor/',
+			'*.txt',
+		),
+	), Arrays::merge($config, $default));
+
+});
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
new file mode 100644
index 0000000..893e8d2
--- /dev/null
+++ b/tests/bootstrap.php
@@ -0,0 +1,11 @@
+<?php
+
+require __DIR__ . '/../vendor/autoload.php';
+
+Tester\Environment::setup();
+
+
+function test($cb)
+{
+	$cb();
+}
diff --git a/tests/php-unix.ini b/tests/php-unix.ini
new file mode 100644
index 0000000..7575ed0
--- /dev/null
+++ b/tests/php-unix.ini
@@ -0,0 +1,2 @@
+[Zend]
+zend_extension=xdebug.so