复制Verify.class.php为Mobile.class.php
修改164行为
$code[$i] = $this->codeSet[$i];
$config = array('length' => 11);
$Verify = new \Think\Mobile($config);
// 设置验证码字符为纯数字
$Verify -> codeSet = '13999999999';
$Verify -> entry(); 