public function verify_c(){

    $Verify = new \Think\Verify();

    $Verify->fontSize = 18;

    $Verify->length   = 4;

    $Verify->useNoise = false;

    $Verify->codeSet = '0123456789';

    $Verify->imageW = 130;

    $Verify->imageH = 50;

    //$Verify->expire = 600;

    $Verify->entry();

}

<p class="top15 captcha" id="captcha-container">

  <input name="verify" width="50%" height="50" class="captcha-text" placeholder="验证码" type="text">

  <img width="30%" class="left15" height="50" alt="验证码" src="{:U('Home/Index/verify_c',array())}" title="点击刷新">

</p>

    $(function () {

        var captcha_img = $('#captcha-container').find('img')

        var verifyimg = captcha_img.attr("src");

        captcha_img.attr('title', '点击刷新');

        captcha_img.click(function(){

            if( verifyimg.indexOf('?')>0){

                $(this).attr("src", verifyimg+'&random='+Math.random());

            }else{

                $(this).attr("src", verifyimg.replace(/\?.*$/,'')+'?'+Math.random());

            }

        });

    })

function check_verify($code, $id = ""){

    $verify = new \Think\Verify();

    return $verify->check($code, $id);

}

$verify = I('param.verify','');

if(!check_verify($verify)){

    $this->error("亲，验证码输错了哦！",$this->site_url,9);

}