<?php
namespace code;
/**
 * class code
 */
class code
{
  protected $number;//验证码内字符个数
  protected $codetype;//验证码样式
  protected $width;//图像宽
  protected $height;//图像高
  protected $code;//验证码
  protected $image;//图像资源
 
  /**
   * code constructor.
   * @param int $number
   * @param int $codetype
   * @param int $width
   * @param int $height
   */
  public function __construct($number=5, $codetype=2, $width=100, $height=40)
  {
    $this->number = $number;
    $this->codetype = $codetype;
    $this->width = $width;
    $this->height = $height;
    $this->code = $this->createcode();
  }
 
  /**
   * 销毁资源
   */
  public function __destruct()
  {
    imagedestroy($this->image);
  }
 
  /**
   * 外部调用code时触发
   * @param $name
   * @return bool
   */
  public function __get($name)
  {
    if ('code' == $name) {
      return $this->$name;
    } else {
      return false;
    }
  }
 
  /**
   * 生成code
   */
  protected function createcode()
  {
    switch ($this->codetype) {
      case 0:
        $code = $this->getnum();
        break;
      case 1:
        $code = $this->getchar();
        break;
      case 2:
        $code = $this->getnumchar();
        break;
      default:
        die('样式不对');
    }
    return $code;
  }
 
  /**
   * 数字验证码
   * @return string
   */
  protected function getnum()
  {
    $str = join('', range(0,9));
    return substr(str_shuffle($str), 0, $this->number);
  }
 
  /**
   * 字符验证码
   * @return string
   */
  protected function getchar()
  {
    $str = join('', range('a', 'z'));
    $str = $str . strtoupper($str);
    return substr(str_shuffle($str), 0, $this->number);
  }
 
  /**
   * 字符和数字混合验证码
   * @return string
   */
  protected function getnumchar()
  {
    $num = join('', range(0, 9));
    $str = join('', range('a', 'z'));
    $str_big = strtoupper($str);
    $numchar = $num . $str . $str_big;
    return substr(str_shuffle($numchar), 0, $this->number);
  }
 
  /**
   * 生成图像
   */
  protected function createimage()
  {
    $this->image = imagecreatetruecolor($this->width, $this->height);
  }
 
  /**
   * 填充背景色
   */
  protected function fillcolor()
  {
    imagefill($this->image, 0, 0, $this->lightcolor());
  }
 
  /**
   * 浅颜色
   * @return int
   */
  protected function lightcolor()
  {
    return imagecolorallocate($this->image, mt_rand(170, 255), mt_rand(170, 255), mt_rand(170, 255));
  }
 
  /**
   * 深颜色
   * @return int
   */
  protected function darkcolor()
  {
    return imagecolorallocate($this->image, mt_rand(0, 120), mt_rand(0, 120), mt_rand(0, 120));
  }
 
  /**
   * 添加验证码字符
   */
  protected function drawchar()
  {
    $width = ceil($this->width/$this->number);
    for ($i = 0; $i < $this->number; $i++) {
      $x = mt_rand($i * ($width - 5), ($i + 1) * ($width - 5));
      $y = mt_rand(0, $this->height - 15);
      imagechar($this->image, 5, $x, $y, $this->code[$i], $this->darkcolor());
    }
  }
 
  /**
   * 添加干扰点
   */
  protected function drawdisturb()
  {
    for ($i= 0; $i < 100; $i++) {
      imagesetpixel($this->image, mt_rand(0, $this->width), mt_rand(0, $this->height), $this->darkcolor());
    }
  }
 
  /**
   * 添加干扰线
   */
  protected function drawarc()
  {
    for ($i = 0; $i < $this->number - 3; $i++) {
      imagearc($this->image, mt_rand(5, $this->width), mt_rand(5, $this->height), mt_rand(5, $this->width), mt_rand(5, $this->height),mt_rand(0, 70), mt_rand(300, 360), $this->darkcolor());
    }
  }
 
  /**
   * 输出显示
   */
  protected function show()
  {
    header('content-type:image/png');
    imagepng($this->image);
  }
 
  /**
   * 外部image
   */
  public function outimage()
  {
    $this->createimage();//创建画布
    $this->fillcolor();//填充背景色
    $this->drawchar();//添加验证字符
    $this->drawdisturb();//添加干扰点
    $this->drawarc();//添加干扰线
    $this->show();//输出
  }
}

<?php
include './code/code.php';
 
$code = new code\code();
$code->outimage();
session_start();
$_session['code'] = [
  'code' => $code->code,
  'exp_time' => time() + (60 * 60 * 10),
];