PHP Object Oriented Array class

gistfile1.inc

<?php

class A implements ArrayAccess, Iterator, Countable
{
   public function __construct($arr) {
     $this->arr = is_array($arr) ? $arr : func_get_args();
   }
   public function __toString() {
     return print_r($this->arr, true);
   }
   public function to_a(){
    return $this->arr;
   }
   public function each(Closure $fun) {
     foreach ($this->arr as $key => $value) 
       $fun($value, $key);
   }
   public function reduce(Closure $fun) {
     $new = array();
     foreach ($this->arr as $key => $value) {
       if($fun($value, $key))
         $new[$key] = $value;
     }
     return $new;
   }
   public function map(Closure $fun) {
     $new = array();
     foreach ($this->arr as $key => $value) 
       $new[$key] = $fun($value, $key);
     return $new;
   }
   public function until(Closure $fun) {
     foreach ($this->arr as $key => $value){
       if($fun($value, $key))
         return $key;
     }
     return false;
   }
   public function __call($name, $args) {
     if(strpos($name, '_') === 0 && is_callable(array($this, substr($name, 1)))) { // leading underscore denotes array reference
       $ret = call_user_func_array(array($this, substr($name, 1)), $args);
       if (is_array($ret)) 
         $this->arr = $ret;
       return $ret;
     } 
     throw new Exception('Call to undefined method '.get_class($this).'::'.$name);
   }
   public function __invoke($i, $length = null) {
     if (!array_key_exists($i, $this->arr)) 
       return null;
     if (is_null($length)) 
      return $this->arr[$i];
     return array_slice($this->arr, $i, $length);
   }
    public function offsetSet($offset,$value) {
        if ($offset == "") {
            $this->arr[] = $value;
        }else {
            $this->arr[$offset] = $value;
        }
    }
    public function offsetExists($offset) {
     return isset($this->arr[$offset]);
    }
    public function offsetUnset($offset) {
        unset($this->arr[$offset]);
    }
    public function offsetGet($offset) {
        return isset($this->arr[$offset]) ? $this->arr[$offset] : null;
    }
    public function rewind() {
        reset($this->arr);
    }
    public function current() {
        return current($this->arr);
    }
    public function key() {
        return key($this->arr);
    }
    public function next() {
        return next($this->arr);
    }
    public function valid() {
        return $this->current() !== false;
    }    
    public function count() {
     return count($this->arr);
    }
}