Get the value of the field?

[Hugilore111]

Hello everybody
how to get value from this field?

<input type="text" name="{$fieldMap.username}" value="{$fields.username}" class="textCtrl" id="ctrl_{$fieldMap.username}" autofocus="true" autocomplete="off" />
            <p class="explain">{xen:phrase this_is_name_that_will_be_shown_with_your_messages}</p>

By default, it is impossible to take

$Name = $this->_input->filterSingle('username', XenForo_Input::STRING);

help me please