feat(pdo): add DD_TRACE_PDO_PREPARED_STATEMENTS_ENABLED and DD_TRACE_PDO_LIFECYCLE_COMMANDS_ENABLED

[jbdelhommeau]

Summary

Add two complementary PHP PDO configuration variables that mirror the Go tracer's WithIgnoreQueryTypes() options:

1. DD_TRACE_PDO_PREPARED_STATEMENTS_ENABLED — suppress PDO.prepare + PDOStatement.execute spans
2. DD_TRACE_PDO_LIFECYCLE_COMMANDS_ENABLED — suppress connection and transaction lifecycle spans

Motivation

The Go tracer exposes fine-grained control over which DB operation types are traced via WithIgnoreQueryTypes(QueryType...). PHP had no equivalent. In high-throughput applications:

• Prepared statement spans (PDO.prepare + execute) can generate noise when the query text is already visible on PDO.exec/PDO.query
• Lifecycle spans (__construct, beginTransaction, commit, rollBack) have low diagnostic value in normal operation but contribute to trace volume

Both flags follow the same pattern already established for Redis (DD_TRACE_REDIS_LIFECYCLE_COMMANDS_ENABLED).

Go tracer equivalence

PHP variable	Go equivalent
DD_TRACE_PDO_PREPARED_STATEMENTS_ENABLED=false	WithIgnoreQueryTypes(QueryTypePrepare)
DD_TRACE_PDO_LIFECYCLE_COMMANDS_ENABLED=false	WithIgnoreQueryTypes(QueryTypeConnect, QueryTypeBegin, QueryTypeCommit, QueryTypeRollback)

Note: unlike Go (code-level option), PHP exposes these as environment variables — configurable without redeployment.

Behaviour

DD_TRACE_PDO_PREPARED_STATEMENTS_ENABLED

Span	true (default)	false
PDO.prepare	✅	❌
PDOStatement.execute	✅	❌
PDO.exec / PDO.query	✅	✅

DD_TRACE_PDO_LIFECYCLE_COMMANDS_ENABLED

Span	true (default)	false
PDO.__construct	✅	❌
PDO.connect	✅	❌
PDO.beginTransaction	✅	❌
PDO.commit	✅	❌
PDO.rollBack	✅	❌
PDO.exec / PDO.query / prepared statements	✅	✅

Note: connection metadata (out.host, db.system, etc.) is always preserved via ObjectKVStore so data command spans keep their tags regardless of the lifecycle flag.

Implementation scope

• ext/configuration.h — two new CONFIG(BOOL, ...) declarations
• src/DDTrace/Integrations/PDO/PDOIntegration.php — per-call flag checks via install_hook; beginTransaction and rollBack added as new traced methods
• metadata/supported-configurations.json — document both variables
• tests/Integrations/PDO/PDOTest.php — regression tests for both flags