What is an eID in the context of TYPO3?

Question

I have come across this term several times. Often the resources jump right into explaining how to do something but do not mention what this is or what it is for. Also, a bunch of resources are in German or not very clear.

So,

• What is an eID?
• Is this a TYPO3 specific thing or is it a general concept?
• What can you do with it?
• Is this still relevant for TYPO3 >= 9?

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Examples resources:

Either build a plugin you can put on your site, or an eID that does not need a site to function.

https://stackoverflow.com/a/18593815/2444812

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This resource actually explains it (though in German), but the code looks terribly outdated.

https://www.webmasterpro.de/coding/article/cms-typo3-eid-mechanismus.html

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btw, there is a tag eID on Stack Overflow but it is for Electronic Identity Card :(

Answer 1

The eID mechanism is an outdated approach to have a custom frontend request handler. The default request handling invokes the TypoScriptFrontendController to render pages and content as usual.

Compared to that an eID script can perform arbitary actions to generate output and is not bound to the regular rendering. In fact, eID scripts are executed with a very minimal environment so every dependency (e.g. parsed TypoScript setup) must be loaded manually. There is the EidUtility for common tasks.

Nowadays eID is not necessary anymore since PSR-15 (Middlewares) has been implemented in TYPO3v9. This provides a way cleaner API and makes it easy to inject custom logic anywhere in the frontend request handling, either to perform completely custom output or intercept and modify the default response generated by the TypoScriptFrontendController.

So if possible, middlewares should be used instead of eID scripts.