<?php $form=ActiveForm::begin([

        'id'=>'login-form',//基本配置
      'action'=>['article/add'],  
        'method'=>'post',

        'options'=>[

            'class'=>'login-form',
         'enctype'=>'multipart/form-data',

        ],

        'fieldConfig'=>[

            'template'=>'{label}<div class="input-icon"><i class="fa fa-user"></i>{input}{error}</div>',

            'labelOptions'=>['class'=>"control-label visible-ie8 visible-ie9"],
        'options'=>[
            'tag'=>'div' 
        ]

        ]

    ]);?>

    <?php echo $form->field($model,'username')->textInput(['class'=>'form-control placeholder-no-fix','autocomplete'=>'off','placeholder'=>'用户名']);?>

    <?php echo $form->field($model,'password')->passwordInput(['class'=>'form-control placeholder-no-fix','autocomplete'=>'off','placeholder'=>'密码']);?>

    <?php echo Html::submitButton('登录',['class'=>'btn green pull-right']);?>

<?php ActiveForm::end();?>

use yii\bootstrap\ActiveForm;

$form = ActiveForm::begin(['layout' => 'horizontal']);

// 隐藏form的标签 
echo $form->field($model, 'demo', [
    'inputOptions' => [
         'placeholder' => $model->getAttributeLabel('demo'),
     ],
 ])->label(false);
 
 // 内联 radio list
 echo $form->field($model, 'demo')->inline()->radioList($items);
 
 //水平模式控制文本框的大小
 echo $form->field($model, 'demo', [
     'horizontalCssClasses' => [
         'wrapper' => 'col-sm-2',
     ]
 ]);
 
 // 除了'default（默认）' 布局 你还可以用 'template' 制定特定的布局:
 echo $form->field($model, 'demo', [
    'template' => '{label} <div class="row"><div class="col-sm-4">{input}{error}{hint}</div></div>'
 ]);
 
 // 自定义输入框的结构
 echo $form->field($model, 'demo', [
    'inputTemplate' => '<div class="input-group"><span class="input-group-addon">@</span>{input}</div>',
 ]);
 
 ActiveForm::end();