一个php的验证码类

<?php
class verificationCode{

	private $image;
	private $width;
	private $height;
	private $pixersum; //干扰点的数目
	private $codenum;//验证字符数目
	private $codes;//字符

	function __construct($width="100", $height="50", $codenum="4"){
		$this->width=$width;
		$this->height=$height;
		$this->codenum=$codenum;
		$this->codes=$this->strings();
		$this->image=imagecreatetruecolor($this->width, $this->height);
		$this->pixersum=floor($width*$height/50);
	}

	function showCode(){
		//画布颜色
		$this->bulidcolor();
		//画干扰素
		$this->bulidgrs();
		//画字符
		$this->bulidzifu();
		//输出并销毁
		$this->show();
	}

	function tocode(){
		return $this->codes;
	}

	private function bulidcolor(){
		//背景颜色
		$red=rand(220, 255);
		$green=rand(220, 255);
		$bule=rand(220, 255);
		$color=imagecolorallocate($this->image, $red, $green, $bule);
		imagefill($this->image, 0, 0, $color);
		//黑色边框
		imagerectangle($this->image, 0, 0, $this->width-1, $this->height-1, imagecolorallocate($this->image, 0, 0, 0));
	}

	private function bulidgrs(){
		
		//画点
		for($i=0; $i<$this->pixersum; $i++){
			$color=imagecolorallocate($this->image, rand(0, 255), rand(0, 255), rand(0, 255));	
			imagesetpixel($this->image, rand(1, $this->width-2), rand(1, $this->height-2), $color);
		}
		//画弧线
		for($i=0; $i<15; $i++){
			$color=imagecolorallocate($this->image, rand(0, 255), rand(0, 255), rand(0, 255));
			imagearc($this->image, rand(-10, $this->width), rand(-10, $this->height), rand(10, $this->width), rand(10, $this->height), rand(-30, 30), rand(-30, 30), $color);
		}
	
	}

	private function strings(){
		$str="1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
		$strs="";
		for($i=0; $i<$this->codenum; $i++){
			$cha=$str{rand(0, strlen($str)-1)};
			$strs.=$cha;
		}
		return $strs;
	}

	private function bulidzifu(){
		for($i=0; $i<$this->codenum; $i++){
		$fontcolor=imagecolorallocate($this->image, rand(0, 128), rand(0, 128), rand(0, 128));
		$fontsize=rand(4, 5);
		$x=floor($this->width/$this->codenum)*$i+3;
		$y=rand(0, $this->height-15);
		imagechar($this->image, $fontsize, $x, $y, $this->codes{$i},$fontcolor);
		}
	
	}

	private function show(){
		header("Content-Type:image/gif");
		imagegif($this->image);
		imagedestroy($this->image);
	}
}
?>