php-Controller is executed two times in succession

Php

The problem is that, send a registration activation email to the user's mailbox, click on the email is the activation link, the result, the controller was executed two times, the chain to copy to the address bar return, the normal execution once, only found that the Firefox browser has this problem, other browsers after the initial test is normal, very strange ah:
/**
* Mailbox Activation
*/
Public Function Active_user () {
File_put_contents (' active.txt ', ' Test mailbox ', file_append);
Die
}
Results Active.txt inside: Test mailbox Test Mailboxes, that has been executed two times, for explanation???
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