src/Web/Sessions/Session.php
public function set($key, $value)
    {
        $this->open();
        $data = $this->data;
        $data[$key] = $value;
        $this->data = $data;
    }
public function set($key, $value)
    {
        $this->open();
        $data = $this->data;
        $data[$key] = $value;
        $this->data = $data;
    }
Adds a session variable.
If the specified name already exists, the old value will be overwritten.
@param string $key session variable name
@param mixed  $value session variable value