php验证码

<?session_start();//生成验证码图片Header("Content-type: image/PNG");$im = imagecreate(44,18);$back = ImageColorAllocate($im, 245,245,245);imagefill($im,0,0,$back); //背景srand((double)microtime()*1000000);//生成4位数字for($i=0;$i<4;$i++){$font = ImageColorAllocate($im, rand(100,255),rand(0,100),rand(100,255));$authnum=rand(1,9);$vcodes.=$authnum;imagestring($im, 5, 2+$i*10, 1, $authnum, $font);}for($i=0;$i<100;$i++) //加入干扰象素{ $randcolor = ImageColorallocate($im,rand(0,255),rand(0,255),rand(0,255));imagesetpixel($im, rand()%70 , rand()%30 , $randcolor);} ImagePNG($im);ImageDestroy($im);$_SESSION['VCODE'] = $vcodes;?>