Data objects and PhpStorm

I am currently testing the use of data objects.
Here is an example:
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class data implements arrayaccess {
    protected $firstname = null;
    protected $lastname = null;
    protected $street = null;

    public  function offsetSet($key, $value)
    {
        if(isset($key, $this)){
            $this->$key = $value;

            return true;
        }

        return false;
    }

    public function offsetGet($key)
    {
        if(!isset($this->$key) or empty($this->$key))
            return false;

        return $this->$key;
    }

    public function offsetUnset($key)
    {
        if(isset($this->$key)){
            $this->$key = null;

            return true;
        }

        return false;
    }

    public function offsetExists($key)
    {
        if(isset($this->$key) and !empty($this->$key)){
            return true;
        }

        return false;
    }
}
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The data I want to use the data properties.
I'm looking for a way that data using a button in the script to write.



$data = new data();
$data['firstname'] = 'Stephan';
$data['lastname'] = 'Krauss';

// Here i will insert $data['firstname'] with a simple button click
$foo['firstname'] =

Who can help with an idea?

Sincerely yours

Stephan