PHP implements verification code class

<?php
class Code{
// 1. 定义各个成员 有宽、高、画布、字数、类型、画类型
private $width; //宽度
private $height; //高度
private $num; //验证码字数
private $imgType; //生成图片类型
private $Type; //字串类型 1,2,3 三个选项 1 纯数字 2 纯小写字母 3 大小写数字混合
private $hb; //画布
public $codestr; // 验证码字串
public function __construct($height=20,$num=4,$imgType="jpeg",$Type=1){
$this->width = $num*20;
$this->height = $height;
$this->num = $num;
$this->imgType = $imgType; 
$this->Type = $Type; 
$this->codestr = $this->codestr();
$this->zuhe();
}
// 2. 定义随机获取字符串函数
private function codestr(){
switch($this->Type){
case 1: // 类型为1 获取1-9随机数
$str = implode("",array_rand(range(0,9),$this->num));
break;
case 2: // 类型为2 获取a-z随机小写字母
$str = implode("",array_rand(array_flip(range(a,z)),$this->num));
break;
case 3: // 类型为3 获取数字,小写字母,大写字母 混合
for($i=0;$i<$this->num;$i++){
$m = rand(0,2);
switch($m){
case 0:
$o = rand(48,57);
break;
case 1:
$o = rand(65,90);
break;
case 2:
$o = rand(97,122);
break; 
}
$str .= sprintf("%c",$o);
}
break; 
}
 
return $str; 
}
 
// 3. 初始化画布图像资源
private function Hb(){
$this->hb = imagecreatetruecolor($this->width,$this->height); 
}
// 4. 生成背景颜色
private function Bg(){
return imagecolorallocate($this->hb,rand(130,250),rand(130,250),rand(130,250)); 
}
// 5. 生成字体颜色
private function Font(){
return imagecolorallocate($this->hb,rand(0,100),rand(0,100),rand(0,100)); 
}
// 6. 填充背景颜色
private function BgColor(){
imagefilledrectangle($this->hb,0,0,$this->width,$this->height,$this->Bg()); 
}
// 7. 干扰点
private function ganrao(){
$sum=floor(($this->width)*($this->height)/3);
for($i=0;$i<$sum;$i++){
imagesetpixel($this->hb,rand(0,$this->width),rand(0,$this->height),$this->Bg()); 
}
}
// 8. 随机直线 弧线
private function huxian(){
for($i=0;$i<$this->num;$i++){
imageArc($this->hb,rand(0,$this->width),rand(0,$this->height),rand(0,$this->width),rand(0,$this->height),rand(0,360),rand(0,360),$this->Bg()); 
} 
}
// 9. 写字
private function xiezi(){
for($i=0;$i<$this->num;$i++){
$x=ceil($this->width/$this->num)*$i; 
$y=rand(1,$this->height-15);
imagechar($this->hb,5,$x+4,$y,$this->codestr[$i],$this->Font());
} 
}
// 10. 输出
private function OutImg(){
$shuchu="image".$this->imgType; 
$header="Content-type:image/".$this->imgType;
if(function_exists($shuchu)){
header($header);
$shuchu($this->hb); 
}else{
exit("GD库没有此类图像"); 
}
}
// 11. 拼装
private function zuhe(){
$this->Hb();
$this->BgColor();
$this->ganrao();
$this->huxian();
$this->xiezi();
$this->OutImg(); 
}
public function getCodeStr(){
return $this->codestr; 
}
}
 
$a = new Code();
$a ->getCodeStr();
?>