code: private function createCode()
      {
          $fontsize = 140;
          for($i=0;$i < $this->number;$i++){
              //设置字体大小  
              //设置字体颜色，随机颜色
              $fontcolor = imagecolorallocate($this->image, rand(0,120),rand(0,120), rand(0,120));      //0-120深颜色
              //设置数字
              $fontcontent = $this->createNumber();
              //10>.=连续定义变量
              $this->captcha_code .= $fontcontent;
              //设置坐标
              $x = ($i*100/4)+rand(5,10);
              $y = rand(5,10);
              imagestring($this->image,$fontsize,$x,$y,$fontcontent,$fontcolor);
          }
          $this->setSession()->disturb();
      }
docs: @name 设置数字