Thinkphp comes with a comprehensive analysis of the verification code

<div style="position:absolute;z-index:3;top:160px;left:180px;">
<img style="cursor:pointer; " src="{:U('Verify')}" onclick="this.src=this.src+'?'+Math.random()" id="safecode" style="height:50px;width:70%;"/>
</div> 
//验证码判断
public function Verify(){
ob_clean();
//显示验证码
$cfg=array(
'codeSet' => '0123456789', // 验证码字符集合
'imageH' => 25, // 验证码图片高度
'imageW' => 80, // 验证码图片宽度
'length' => 4, // 验证码位数
'fontttf' => '4.ttf', // 验证码字体，不设置随机获取
'fontSize' => 10, // 验证码字体大小(px)
'useNoise' => false, // 是否添加杂点
'useCurve' => false, // 是否画混淆曲线
'bg' => array(226,229,236) //背景颜色
);
$very=new \Think\Verify($cfg);
$very->entry();
} 
//客户端通过ajax，实现校验验证码
public function checkVerify(){
$code = I('get.code');
$very = new \Think\Verify();
$key = $this->auth_my_code($very,$very->seKey);
// 验证码不能为空
$secode = session($key);
//对$code进行加密，在比较校验
if($this->auth_my_code($very,strtoupper($code)) == $secode['verify_code']) {
echo json_encode(array('flag'=>1,'cont'=>'验证码正确'));
}else{
echo json_encode(array('flag'=>2,'cont'=>'验证码错误'));
}
}
private function auth_my_code($vry,$str){
$key = substr(md5($vry->seKey), 5, 8);
$str = substr(md5($str), 8, 10);
return md5($key . $str);
}

else{
$('#safecode').attr("src","/Login/Verify?"+Math.random());
NewAlert(2,"验证码有误，请重新输入",null);
code_ok = false;
$('#verifyresult').html(msg.cont).css({'color':'red','font-size':'12px'}); 
}