Public function verify(){
  // 导入Image类库
  import("ORG.Util.Image");
  Image::buildImageVerify();
}

import("@.Util.Image");

<input type="text" name="verify">
<img id="verifyImg" src="-Article-verify" onClick="changeVerify()" title="点击刷新验证码" />

<script language="JavaScript">
function changeVerify(){
 var timenow = new Date().getTime();
 document.getElementById('verifyImg').src='-Article/verify/'+timenow; 
}
</script>

if($_SESSION['verify'] != md5($_POST['verify'])) {
  $this->error('验证码错误！');
}

/** 
 * 
 * 验证码生成 
 */ 
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> 

// 验证码生成 
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()); 
  } 
}); 

/** 
 * 验证码检查 
 */ 
function check_verify($code, $id = ""){ 
  $verify = new \Think\Verify(); 
  return $verify->check($code, $id); 
} 

// 检查验证码 
$verify = I('param.verify',''); 
if(!check_verify($verify)){ 
  $this->error("亲，验证码输错了哦！",$this->site_url,9); 
}