There is no EOL planned for PHP 5.6, as of today. But when the EOL is announced, the particular version that is deprecated will be supported for 2 years from the announcement date.

2. How will future upgrades for PHP roll out work?

All major and minor versions of PHP will be supported in Oracle B2C Service upon release. The micro version will be upgraded whenever Common Vulnerabilities and Exposures (CVEs) are reported and fixed in the micro version.

3. How often will PHP scripts need to be migrated to a new version in future?

Migrating to a PHP version is a customer decision. We want to provide that flexibility to customers and thus have completed the Support for Multiple PHP versions in Oracle B2C Service product. We allow customers to upgrade their base PHP version on their timeline and under their control.

4. What is the sub-version supported for 8.3? like 8.3.19, 8.3.20 etc.?

Please see details below. Every release we pick up the patch version

24C, 24D -> 8.3.6

25A -> 8.3.12

25B -> 8.3.15

25C -> 8.3.20 (or latest release before May 2nd week)

5. Is there a tool that Oracle can recommend to be used to quickly identify the incompatible methods, syntax etc. to speed up the process?

The tool at https://onlinephp.io/ can be used to see the difference in behavior. https://github.com/PHPCompatibility/PHPCompatibility is another tool that can do static code analysis and find out compile time issues.