Summary

As part of rebasing EDOT PHP on the upstream opentelemetry-php-distro submodule, all distro-specific configuration options now use the upstream OTEL_PHP_* / opentelemetry_distro.* naming convention as the preferred form. The previous ELASTIC_OTEL_* / elastic_otel.* names continue to work as deprecated fallbacks via ElasticConfigProvider.

The documentation needs to be updated to reflect this change.

Changes

configuration.md

• Rename section "Options only available in EDOT PHP" → "EDOT PHP distro configuration options"
• Add deprecation notice explaining both naming conventions and precedence rules
• Update all option tables to use OTEL_PHP_* as primary names
• Add deprecated aliases below each table
• Update tab-set examples to show both preferred and deprecated forms (env vars and php.ini)

migration.md

• Update "Update configuration" step table (ELASTIC_OTEL_ENABLED → OTEL_PHP_ENABLED)
• Update full "Configuration mapping" table to use OTEL_PHP_* names

deprecations.md

• Add deprecation entry for version 1.5.0 listing all renamed options
• Full mapping table of all 29 deprecated ELASTIC_OTEL_* → OTEL_PHP_* equivalents

DEVELOPMENT.md

• Add "Repository structure" section describing the upstream submodule layout
• Add "Contributing changes" section (non-Elastic changes go to upstream repo)
• Fix all paths from prod/native/ → upstream/prod/native/
• Add -DCMAKE_PROJECT_INCLUDE to manual cmake build commands
• Replace duplicated sections (docker images, conan, PHP deps) with references to upstream docs

Context

This is part of the broader effort to rebase EDOT PHP on the upstream opentelemetry-php-distro as a git submodule (#352 ). The native layer implements backward compatibility through ElasticConfigProvider, which falls back to ELASTIC_OTEL_* env vars and elastic_otel.* INI entries when the upstream OTEL_PHP_* / opentelemetry_distro.* values are not set. If both are set, the upstream name takes precedence.