@Kavya Batchu We understand that you are attempting to update your Linux Web App from PHP 7.4 to PHP 8.0 but encountering a 404 error after doing so.
Please note that you technically have time as php 7.4 apps will continue to run, even after 11/28. This is verified where it's shared, "Extended support for PHP 7.4 will end on November 28, 2022. After this date, your applications will continue to run, however any application hosted in App Service targeting PHP 7.4 will be out of support and at risk of security vulnerabilities that remain unpatched." Source
In regard to the 404 error that you are receiving after updating your php 7.4 app to php 8, have you updated the target stack from PHP 7.4 to PHP 8.0 in the Azure Portal for your web app?
Note that changing your runtime will trigger a restart of your web app.
Update your App Service apps to use a supported version of PHP in the Azure portal:
- In the Azure portal, click the App Service blade. Select the app you want to update.
- In the Configuration panel, click the General settings tab.
- Under Stack Settings, click the drop-down menu under Minor version and select the PHP version you want (we recommend choosing the most recent version).
- Click Save.
Please let us know if the above setting change resolves the issue.