<?php

	/**

	 * 该类实例化的时候需要3个参数

	 * $width;//验证码的宽,默认值为80px

	 * $height;//验证码的高,默认值为20px

	 * $num;//验证码字符的个数,默认值为4

	 */

	class Code{

		private $width;//验证码的宽

		private $height;//验证码的高

		private $num;//验证码字符的个数

		private $code;//验证码的字符串

		private $img;//验证码source

		function __construct($width=80,$height=20,$num=4){

			$this->width=$width;

			$this->height=$height;

			$this->num=$num;

			$this->code=$this->create_code();

		}

		private function create_canvas(){//创建画布

			$this->img=imagecreatetruecolor($this->width,$this->height);

			$background_color=imagecolorallocate($this->img,0xFF,0xFF,0xFF);

			imagefill($this->img,0,0,$background_color);

			$border_color=imagecolorallocate($this->img,0xAA,0xAA,0xAA);

			imagerectangle($this->img,0,0,$this->width-1,$this->height-1,$border_color);

		}

		private function create_code(){//生成验证码的字符串

			$src="3456789qwertyupkjhgfdsazxcvbnmQWERTYUPLKJHGFDSAZXCVBNM";

			$code="";

			for($i=0;$i<$this->num;$i++){

				$index=mt_rand(0,strlen($src)-1);

				$code.=$src[$index];

			}

			return $code;

		}

		private function paint_char(){//将生成的字符串画在画布上

			for($i=0;$i<$this->num;$i++){

				$char_color=imagecolorallocate($this->img,0xFF,0,0xFF);

				$font_size=4;

				$x=5+($this->width/$this->num)*$i;

				$y=($this->height-imagefontheight($font_size))/2;

				imagechar($this->img,$font_size,$x,$y,$this->code[$i],$char_color);

			}

		}

		private function add_disturbance(){//添加干扰标记

			for($i=0;$i<20;$i++){

				$color=imagecolorallocate($this->img,rand(0,255),rand(0,255),rand(0,255));

				imagesetpixel($this->img,rand(1,$this->width-2),rand(1,$this->height-2),$color);

			}

		}

		private function print_code() {//判断兼容哪种格式

			if (imagetypes() & IMG_PNG) {

   				header("Content-type: image/png");

    			imagepng($this->img);

			} elseif (imagetypes() & IMG_JPG) {

   				header("Content-type: image/jpeg");

    			imagejpeg($this->img);

			}  else {

  				  die("No image support in this PHP server");

			}

		}

		private function get_code(){//获取验证码字符串的值

			return $this->code;

		}

		private function destroy_code(){//释放资源

			imagedestroy($this->img);

		}

		function show_image_code(){//所有步骤的汇集，搞定所有验证码的工作

			$this->create_canvas();

			$this->paint_char();

			$this->add_disturbance();

			$this->print_code();

			$this->destroy_code();

		}

	}

	//测试

	$code = new Code(80, 30, 4);

	$code->show_image_code();

 ?>