I recently got a request to install a PHP extension in an Azure Web Service running PHP 7.1, Cake PHP and MySQL. The extension to install was Imagick 3.4.3 x64, which is used for all kinds of image manipulation. The marketplace extension Composer was installed already.
Since Azure Web Service is a managed service, installing non-marketplace extensions is not as straight forward as on a managed machine running Windows or Linux. But even though the required steps are not officially documented, there are some resources available on the issue. I used the following manual.

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