Some browsers cache the CAPTCHA, causing the verification code to expire when the page is reopened.

Refreshing the browser is normal.
How to solve, what code can force the verification code re-loaded.

Reply to discussion (solution)

Add a js random parameter after the generated address, url?r=math.random ()

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You add a non-cached header to the CAPTCHA picture generator

Header ("Expires:mon, Jul 1997 05:00:00 GMT");    Date in the Pastheader ("Last-modified:". Gmdate ("D, D M Y h:i:s"). "GMT"); Header ("Cache-control:no-cache, must-revalidate");  Http/1.1header ("Pragma:no-cache");                          http/1.0

You can solve this problem once and for all without having to change the URL every time you use it.

Math.random ()

Already, but no, now the code is:

Plus, it's not going to work.

You add a non-cached header to the CAPTCHA picture generator

Header ("Expires:mon, Jul 1997 05:00:00 GMT");    Date in the Pastheader ("Last-modified:". Gmdate ("D, D M Y h:i:s"). "GMT"); Header ("Cache-control:no-cache, must-revalidate");  Http/1.1header ("Pragma:no-cache");                          http/1.0

You can solve this problem once and for all without having to change the URL every time you use it.

I can't add this.

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