Yii2 验证码

<div class="col-sm-12 login">
<div class="row">
<div class="col-sm-6 col-md-offset-3">
<?php $form = ActiveForm::begin([
'fieldConfig' => [
'template' => '<div class="form-group"><label for="inputPassword3" class="col-sm-4 control-label">{label}：</label> <div class="col-sm-8 b-margin10">{input}<label class="xz_b">{error}</label></div></div>',
'inputOptions' => ['class' => 'form-control'],
'labelOptions' => ['class' => ''],
],
'options' => ['class' => 'form-horizontal']
]); ?>
<?= $form->field($model, 'username')->textInput(['placeholder' => '6~8个字符，可使用字母、数字，需以字母开头。']) ?>
<?= $form->field($model, 'verifyCode')->widget(yii\captcha\Captcha::className(), [
'template' => '<div class="col-sm-9 padding0">{input}</div><div class="col-sm-3 "><label >{image}</label></div> ',
'imageOptions' => ['id' => 'checkpic', 'title' => '点击换图', 'style' => 'cursor:pointer', 'class' => 'yzm', 'onclick' => 'changing();'],
]) ?>

<?= $form->field($model, 'password')->passwordInput(['placeholder' => '6~16个字符，区分大小写。']) ?>
<?= $form->field($model, 'replace_password')->passwordInput() ?>
<div class="row text-center">
<div class="col-lg-12">
<button type="submit" class="btn btn-primary btn-lg btn-neir">下一步</button>
</div>
</div>
<?php $form = ActiveForm::end() ?>
</div>
</div>
</div>

<script type="text/javascript">
//更改或者重新加载验证码
function changing() {
$.ajax({
url: "/site/captcha?refresh",
dataType: 'json',
cache: false,
success: function(data) {
$("#checkpic").attr('src', data['url']);
}
});
}
</script>