<?php
/** Captcha 驗(yàn)證碼類
*	Date: 	2011-02-19
*	Author:	fdipzone
*/
class Captcha{	//class start
	private $sname = &#39;&#39;;
	public function __construct($sname=&#39;&#39;){	// $sname captcha session name
		$this->sname?=?$sname==''??'m_captcha'?:?$sname;
	}
	/**?生成驗(yàn)證碼圖片
	*?@param??int	$length?驗(yàn)證碼長(zhǎng)度
	*?@param??Array	$param??參數(shù)
	*?@return?IMG
	*/
	public?function?create($length=4,$param=array()){
		Header("Content-type:?image/PNG");
		$authnum?=?$this->random($length);	//生成驗(yàn)證碼字符.
	
		$width	=?isset($param['width'])??$param['width']?:?13;		//文字寬度
		$height?=?isset($param['height'])??$param['height']?:?18;	//文字高度
		$pnum	=?isset($param['pnum'])??$param['pnum']?:?100;		//干擾象素個(gè)數(shù)
		$lnum	=?isset($param['lnum'])??$param['lnum']?:?2;		//干擾線條數(shù)
		$this->captcha_session($this->sname,$authnum);				//將隨機(jī)數(shù)寫入session
		$pw?=?$width*$length+10;
		$ph?=?$height+6;
				
		$im?=?imagecreate($pw,$ph);						//imagecreate()?新建圖像，大小為?x_size?和?y_size?的空白圖像。
		$black?=?ImageColorAllocate($im,?238,238,238);	//設(shè)置背景顏色
	
		$values?=?array(
				mt_rand(0,$pw),??mt_rand(0,$ph),
				mt_rand(0,$pw),??mt_rand(0,$ph),
				mt_rand(0,$pw),??mt_rand(0,$ph),
				mt_rand(0,$pw),??mt_rand(0,$ph),
				mt_rand(0,$pw),??mt_rand(0,$ph),
				mt_rand(0,$pw),??mt_rand(0,$ph)
		);
		imagefilledpolygon($im,?$values,?6,?ImageColorAllocate($im,?mt_rand(170,255),mt_rand(200,255),mt_rand(210,255)));	//設(shè)置干擾多邊形底圖
	
		/*?文字?*/
		for?($i?=?0;?$i?< strlen($authnum); $i++){
			$font = ImageColorAllocate($im, mt_rand(0,50),mt_rand(0,150),mt_rand(0,200));//設(shè)置文字顏色
			$x  = $i/$length * $pw + rand(1, 6);	//設(shè)置隨機(jī)X坐標(biāo)
			$y  = rand(1, $ph/3);					//設(shè)置隨機(jī)Y坐標(biāo)
			imagestring($im, mt_rand(4,6), $x, $y, substr($authnum,$i,1), $font); 
		}
		/* 加入干擾象素 */
		for($i=0; $i<$pnum; $i++){
			$dist = ImageColorAllocate($im, mt_rand(0,255),mt_rand(0,255),mt_rand(0,255)); //設(shè)置雜點(diǎn)顏色
			imagesetpixel($im, mt_rand(0,$pw) , mt_rand(0,$ph) , $dist); 
		} 
		/* 加入干擾線 */
		for($i=0; $i<$lnum; $i++){
			$dist = ImageColorAllocate($im, mt_rand(50,255),mt_rand(150,255),mt_rand(200,255)); //設(shè)置線顏色
			imageline($im,mt_rand(0,$pw),mt_rand(0,$ph),mt_rand(0,$pw),mt_rand(0,$ph),$dist);
		}
		ImagePNG($im);		//以 PNG 格式將圖像輸出到瀏覽器或文件
		ImageDestroy($im);	//銷毀一圖像
	}
	/** 檢查驗(yàn)證碼
	* @param String $captcha	驗(yàn)證碼
	* @param int 	$flag		驗(yàn)證成功后 0:不清除session 1:清除session
	* @return boolean
	*/	
	public function check($captcha,$flag=1){
		if(empty($captcha)){
			return false;
		}else{
			if(strtoupper($captcha)==$this->captcha_session($this->sname)){	//檢測(cè)驗(yàn)證碼
				if($flag==1){
					$this->captcha_session($this->sname,'');
				}
				return?true;
			}else{
				return?false;
			}
		}
	}
	
	/*?產(chǎn)生隨機(jī)數(shù)函數(shù)
	*?@param	int		$length	需要隨機(jī)生成的字符串?dāng)?shù)
	*?@return	String
	*/
	private?function?random($length){
		$hash?=?'';
		$chars?=?'ABCDEFGHIJKLMNPQRSTUVWXYZ23456789';
		$max?=?strlen($chars)?-?1;
		for($i?=?0;?$i?< $length; $i++) {
			$hash .= $chars[mt_rand(0, $max)];
		}
		return $hash;
	}
	/** 驗(yàn)證碼session處理方法
	* @param	String	$name	captcha session name
	* @param	String	$value
	* @return	String
	*/
	private function captcha_session($name,$value=null){
		if(isset($value)){
			if($value!==&#39;&#39;){
				$_SESSION[$name] = $value;
			}else{
				unset($_SESSION[$name]);
			}
		}else{
			return isset($_SESSION[$name])? $_SESSION[$name] : &#39;&#39;;
		}
	}
}	// class end
?>

demo

<?
	session_start();
	require_once(&#39;Captcha.class.php&#39;);
	$obj = new Captcha($sname);		# 創(chuàng)建Captcha類對(duì)象
									# $sname為保存captcha的session name,可留空,留空則為&#39;m_captcha&#39;
	$obj->create($length,$param);	#?創(chuàng)建Captcha并輸出圖片
									#?$length為Captcha長(zhǎng)度，可留空，默認(rèn)為4
									/*?$param?=?array(
											'width'?=>?13		captcha?字符寬度
											'height'?=>?18		captcha?字符高度
											'pnum'?=>?100		干擾點(diǎn)個(gè)數(shù)
											'lnum'?=>?2			干擾線條數(shù)
											)
											可留空
									*/
	$obj->check($captcha,$flag);	#?檢查用戶輸入的驗(yàn)證碼是否正確，true?or?false
									#?$captcha為用戶輸入的驗(yàn)證碼,必填
									#?$flag?可留空，默認(rèn)為1?
									#		1:當(dāng)驗(yàn)證成功后自動(dòng)清除captcha?session
									#		0:當(dāng)驗(yàn)證成功后不清除captcha?session,用於ajax檢查
?>

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