<?php
/**
 * Created by PhpStorm.
 * Author:liuqun@
 * Date: 2018/7/25
 * Time: 0:54
 */
namespace Frame\Vendor;
//定义图片验证码类
final class Captcha
{
  //成员属性
    private  $code;        //验证码字符串
    private  $codelen;     //验证码长度
    private  $width;       //宽度
    private  $height;      //高度
    private  $img;         //图像资源句柄
    private  $fontfile;    //字体文件
    private  $fontsize;    //字体大小
    private  $fontcolor;   //字体颜色

    //构造方法
    public function __construct($codelen=4,$width=85,$height=40,$fontsize=20)
    {
        $this->codelen = $codelen; //验证码字符串长度
        $this->width   = $width;   //图像宽度
        $this->height  = $height;  //图像高度
        $this->fontfile= "./Public/Admin/Images/msyh.ttf";//字体文件
        $this->fontsize= $fontsize;
        $this->createCode();       //创建验证码字符串
        $this->createImg();        //创建图像资源
        $this->createBg();         //创建背景颜色
        $this->createFont();       //绘制文本
        $this->outPut();           //输出图像
    }
    //创建图像资源
    private  function  createImg()
    {
        $this->img = imagecreatetruecolor($this->width,$this->height);
    }

    //生成验证码
    private function createCode()
    {
        $str = "";
        $arr = array_merge(range("a","z"),range("A","Z"),range(0,9));
        shuffle($arr);
        shuffle($arr);
        $arr_index = array_rand($arr,$this->codelen);
        shuffle($arr_index);
        //生成随机字符串
        foreach($arr_index as $i)
        {
            $str .=$arr[$i];
        }
        //将字符串赋给$code属性
        $this->code = $str;
    }
    //生成背景
    private function createBg()
    {
        //随机背景色
        $color = imagecolorallocate($this->img,mt_rand(157,255),mt_rand(157,255),mt_rand(157,255));
        //绘制矩形
        imagefilledrectangle($this->img,0,0,$this->width,$this->height,$color);
    }
    //创建文字
    private function createFont()
    {
        $this->fontcolor = imagecolorallocate($this->img,mt_rand(0,156),mt_rand(0,156),mt_rand(0,156));
        imagettftext($this->img,$this->fontsize,0,5,30,$this->fontcolor,$this->fontfile,$this->code);
    }
    //输出
    private function outPut()
    {
        header("Content-type:image/png");
        imagepng($this->img);
        imagedestroy($this->img);
    }
    //获取验证码
    public function getCode()
    {
        return strtolower($this->code);
    }
}

调用的时候

  引进这个类，（注意引进命名空间）并且将从数据库中取出来的用户信息存储到$_SESSION 中
   //获取验证码方法
    public function captcha()
    {
        //创建验证码类的对象
        $captchaObj = new \Frame\Vendor\Captcha();
        //获取验证码字符串，并存入SESSION
        $_SESSION['captcha'] = $captchaObj->getCode();
    }