php中的nocache是什么意思中的nocache是啥意思
这是在生成验证码的一条语句，captcha.php是生成验证码的脚本。
但在下面这个链接中的评述是：随机参数，一般是为了避免该页面被缓存而设置的
http://topic.csdn.net/u/20090703/15/baf5169e-87f0-478f-8e77-7ae5963d9925.html
这句话我不明白
------解决方案--------------------
浏览器如果开启缓存，一般会把相同url的图片缓存起来，下次访问同一个url的图片就直接显示缓存的文件。
这个既然是验证码，肯定不希望刷新页面它还不变了。所以url后面加个随机数之类的。
------解决方案--------------------
浏览器对于相同的url可能会有缓存(尤其是IE做ajax的时候痛苦死你)，加个的参数避免相同的url。从而防止缓存。大概就是这个意思
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