public function add($key, $element)
    {
        if ($this->has($key) === false) {
            $this->set($key, $element);
        }
    }
public function add($key, $element)
    {
        if ($this->has($key) === false) {
            $this->set($key, $element);
        }
    }
public function add ( $ key , $ element ) { if ( $ this -> has ( $ key ) === false ) { $ this -> set ( $ key , $ element ) ; } }
Adds a new element in this collection.

@param mixed $key     The key associated to the element
@param mixed $element The element
Adds a new element in this collection .