[Sync EN] userlandnaming.xml Explain the identifier, symbol; personalization (#4032)

[github-actions]

Commit: https://github.com/php/doc-en/commit/077012fff21b527d01ffde600ad3282098aa1c91
PR: https://github.com/php/doc-en/pull/4032

Fichiers FR à mettre à jour

• appendices/userlandnaming.xml