$data = array(
              'name'        => 'username',
              'id'          => 'username',
              'value'       => 'johndoe',
              'maxlength'   => '100',
              'size'        => '50',
              'style'       => 'width:50%',
            );

echo form_input($data);

// Would produce:

<input type="text" name="username" id="username" value="johndoe" maxlength="100" size="50" style="width:50%" />