Here's an odd one. On a Windows 10 laptop (build 19042), a webpage at one particular web host suddenly misbehaves in an elementary way: a simple PHP login form that posts to itself fails entirely to post the user's data input---once Submit is clicked, the form repopulates with the browser's saved defaults; it fails to populate the $_POST[] array. $_POST[] remains empty.

The problem occurs with Chrome, Firefox and Microsoft Edge.

It does not occur with other identically coded scripts at the site of this misbehaving script.

It does not occur with the same script running on this machine's Apache webserver, or at another web host.

It does not occur when the problem web script is accessed from a Linux VM running on this WIn10 laptop, or on other machines running varieties of Linux and Windows.

On the problem machine, BitDefender and MalwareBytes find no issues anywhere on the machine, nor in the PHP script itself.

At the problem website, scans find no infection or malware issues.

I'm at a loss. Any ideas/suggestions would be much appreciated.

- - - Updated - - -

In Windows, the problem goes away when such scripts run on the target server with just http rather than https. On other servers, these scripts run fine.


In browsers under Linux, however, there are no such problems.


Ideas anyone?

- - - Updated - - -

It gets odder.

In Windows, the problem goes away when such scripts run on the target server with just http rather than https.

In browsers running in Linux, however, there are no such problems.

Ideas anyone?