No attempt at being canonical

Underscore.php

<?php

namespace common\helpers;

use yii\base\UnknownPropertyException;
use yii\helpers\ArrayHelper;

/**
 * @author Arleigh Dickerson
 *
 * an array helper class to make functional programming more accessible
 *
 * Class Underscore
 * @package fu\core\common\helpers
 */
class Underscore extends \ArrayObject {
    public function filter($predicate) {
        return self::wrap(array_filter((array)$this, $predicate));
    }

    public function map($callback) {
        return self::wrap(array_map($callback, (array)$this));
    }

    public function fold($callback, $initial = null) {
        return self::wrap(array_reduce((array)$this, $callback, $initial));
    }

    public function diff($other) {
        return self::wrap(array_diff((array)$this, $other));
    }

    public function withoutKeys($keys) {
        return self::wrap(array_diff_key((array)$this, array_flip($keys)));
    }

    public function intersect($other) {
        return self::wrap(array_intersect((array)$this, $other));
    }

    public function intersectKey($other) {
        return self::wrap(array_intersect_key((array)$this, $other));
    }

    public function join($glue) {
        return self::wrap(join($glue, (array)$this));
    }

    public function contains($value) {
        return in_array($value, (array)$this);
    }

    public function containsKey($value) {
        return array_key_exists($value, (array)$this);
    }

    public function merge($other) {
        return self::wrap(array_merge((array)$this, (array)$other));
    }

    public function toLower() {
        return $this->map(function ($str) {
            return strtolower((string)$str);
        });
    }

    public function one($default = false) {
        $array = array_values($this->__);
        if ($default === false) {
            $count = count($array);
            assert($count === 1);
        }
        return __($array)->getValue(0, $default);
    }

    public function asSet() {
        return self::wrap(array_combine((array)$this, (array)$this));
    }


    public function __get($name) {
        if ($name === '__') {
            return (array)$this;
        }
        throw new UnknownPropertyException('Getting unknown property: ' . get_class($this) . '::' . $name);
    }

    public function __call($name, $args = []) {
        array_unshift($args, (array)$this);
        return self::wrap(call_user_func_array([ArrayHelper::class, $name], $args));
    }


    private static function wrap($obj) {
        if ($obj instanceof self) {
            return $obj;
        }
        if (is_array($obj)) {
            return new self($obj);
        }
        if ($obj instanceof \ArrayObject) {
            return new self((array)$obj);
        }
        return $obj;
    }
}