Doctrine\Common\Collections\ArrayCollection::offsetExists PHP Method

    public function offsetExists($offset)
    {
        return $this->containsKey($offset);
    }

 /**
  * @return mixed
  */
 public function addAttribute($name, $value)
 {
     if (!$this->attributes->offsetExists($name)) {
         $this->attributes->set($name, $value);
     }
     return $this;
 }