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php生成随机验证码。该如何处理

WBOY
WBOYOriginal
2016-06-13 10:44:241341browse

php生成随机验证码。
for($i=0;$i
  $rand.=dechex(rand(1,15));

}
//设置图像大小
$im=imagecreatetruecolor(100,30);
//设置颜色
$bg=imagecolorallocate($im,0,0,0);
$te=imagecolorallocate($im,255,255,255);
//把字符串写在图像上面
imagestring($im,rand(3,6),rand(3,70),rand(0,16),$rand,$te);
//输出图像
header("Content-type: image/jpeg");
imagejpeg($im);


?>

为何图片显示一个红叉。。
gd库已经打开

------解决方案--------------------

探讨

如何我吧$_SESSION[check]=$rand;注释掉就有用,为什么会这样啊
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