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PHP telemetry agent for the [guard-core](https://github.com/Guard-Core/guard-core) ecosystem. It buffers security events, performance metrics, and agent status in memory (optionally persisted to Redis) and ships them to the Guard Core App ingestion API with at-least-once delivery semantics: nothing acknowledged is lost, nothing unacknowledged is forgotten.

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Ecosystem

Guard Core is the Python engine. Framework adapters are thin wrappers that translate native request/response types into Guard Core's protocols. The telemetry agents ship security events and metrics to the monitoring backend. Parallel engine implementations exist for Go, PHP, TypeScript (on npm), and Rust (on crates.io) - all ports of the same reference semantics, conformance-tested against the shared adversarial corpus.

Python

Package	Role	PyPI
guard-core	Framework-agnostic security engine
guard-agent	Telemetry agent
fastapi-guard	FastAPI / Starlette adapter
flaskapi-guard	Flask adapter
djapi-guard	Django adapter
tornadoapi-guard	Tornado adapter

Go

Go modules published via GitHub releases. Production-ready.

Package	Role	Release
guard-core-go	Go engine
nethttp-guard	net/http adapter
gin-guard	Gin adapter
echo-guard	Echo (v4) adapter
fiber-guard	Fiber (v3) adapter
guard-agent-go	Telemetry agent

PHP

Published on Packagist under the rennf93 vendor. Production-ready.

Package	Role	Packagist
guard-core-php	PHP engine
laravel-guard	Laravel adapter
symfony-guard	Symfony adapter
psr15-guard	PSR-15 adapter
slim-guard	Slim 4 adapter
guard-agent-php	Telemetry agent

TypeScript / JavaScript

Published under the @guardcore npm scope; source in the guard-core-ts monorepo. Production-ready.

Package	Role	npm
	@guardcore/core	Core engine
@guardcore/express	Express adapter
@guardcore/nestjs	NestJS adapter
@guardcore/fastify	Fastify adapter
@guardcore/hono	Hono (edge) adapter
guardagent	Telemetry agent

Rust

Published on crates.io. Production-ready.

Package	Role	crates.io
guard-core-engine	Core engine crate
guard-core-rs	Facade crate (consumer entry point)
actix-guard-rs	Actix Web adapter
axum-guard-rs	Axum adapter
tower-guard-rs	Tower adapter
rocket-guard-rs	Rocket adapter
guard-agent-rs	Telemetry agent

AI Coding Agents

Package	Role	PyPI
guard-core-mcp	MCP server: config validation, docs search, detection sandbox

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Install

composer require rennf93/guard-agent-php

Requires PHP ^8.2, ext-json, and ext-curl. Crash-recovery persistence to Redis works out of the box through a built-in stream client (no extra extension needed); if you already run ext-redis or predis/predis, adapters for both are provided.

Usage

The agent is host-driven: PHP has no background threads, so flush timers run when you call the agent, not behind your back.

use RenzoFranceschini\GuardAgent\Config\AgentConfigResolver;
use RenzoFranceschini\GuardAgent\GuardAgent;

$agent = new GuardAgent(AgentConfigResolver::resolve([
    'apiKey' => $_ENV['GUARD_API_KEY'],
    'endpoint' => 'https://api.guard-core.com',
    'projectId' => 'my-project',
    'payloadSigningSecret' => $_ENV['GUARD_SIGNING_SECRET'] ?? null,
]));

$agent->start();

// From anywhere in your request path: never throws, never blocks (default drop policy).
$agent->sendEvent([
    'event_type' => 'penetration_attempt',
    'ip_address' => $clientIp,
    'endpoint' => '/login',
    'method' => 'POST',
    'metadata' => ['rule' => 'sqli-union-select'],
]);

$agent->sendMetric([
    'metric_type' => 'response_time',
    'value' => 0.023,
    'endpoint' => '/login',
]);

// Ship telemetry at the end of the request (kernel.terminate in Symfony,
// register_shutdown_function in plain PHP, terminate in Laravel).
register_shutdown_function(static function () use ($agent): void {
    $agent->flushBuffer();
    $agent->stop();
});

Long-running workers (CLI daemons, RoadRunner, Swoole-style loops)

Do not reach for pcntl_alarm or extension timers: drive the agent from your own loop with tick(), which flushes when the high-watermark or the flush interval is reached, pushes status reports on the status interval, and refreshes the dynamic rules on the dynamic rule interval.

$agent->start();
while (true) {
    $agent->tick();   // cheap: no network I/O unless a trigger fires
    doWork();
    usleep(1_000_000);
}
$agent->stop();       // final flush, releases Redis

Reliability semantics

• At-least-once handshake: flushBuffer() drains each kind, sends it, and only on success confirms the batch (deleting any Redis records). Transient failures requeue the batch at the front of the buffer in its original order; under pressure the tail (newest items) is evicted and its records confirmed.
• Per-kind backoff: after a failed flush the kind is gated for min(flushInterval * 2^(streak - 1), 300) seconds before the next attempt.
• Circuit breaker: 5 consecutive transport failures in 60 seconds open the circuit; 400/404/413/422 rejections are exempt (they are batch-level, not health signals). 429 counts; Retry-After is honored up to a 300s cap.
• Permanent rejection: 400/404/422 drop the batch (logged and counted, never retried, never thrown). A 413 splits the batch in half and retries each half; a singleton that still exceeds the cap is dropped.
• Partial success is failure: a 200 with success: false or a non-empty errors[] requeues the whole batch.
• Degraded state: the status report reads degraded when the circuit breaker is open, the buffer is at or above 90 percent occupancy, or the lifetime failure rate exceeds 10 percent.
• Failure isolation: no public method ever throws into the host path (the one deliberate, opt-in exception is the block overflow policy). See AGENTS.md for the full contract.

The uncompressed-signature note

When payloadSigningSecret is set, the transport sends X-Payload-Signature: v1=<hex> where <hex> is hash_hmac('sha256', <uncompressed JSON body>, <secret>). The Guard Core App ingestion API verifies the signature after decompressing the body (its GzipRequestMiddleware inflates Content-Encoding: gzip request bodies before the telemetry router runs), so the HMAC must always cover the uncompressed JSON bytes. This differs from the Python/TypeScript/Go agents, which sign the post-gzip bytes and silently fail verification whenever compression kicks in; the PHP agent signs what the server actually verifies.

Dynamic rules

getDynamicRules() returns the SaaS rule document from GET /api/v1/rules as a DynamicRules value object (snake_case wire keys, mirroring the Python agent's pydantic model). The fetched copy is cached in memory and served while it is younger than its own ttl (seconds, default 300); a failed fetch returns null while the last good rules stay cached for the next poll, and a thrown transport error falls back to the cached copy, so a rules outage never surfaces as a hard failure. The tick() loop refreshes the cache every dynamicRuleInterval seconds (default 300, minimum 60). Fetch statistics surface in getStats() as rulesFetched, cachedRules, rulesLastUpdate, and loopFailures.rules.

Encryption

When projectEncryptionKey is set (a urlsafe-base64-encoded 256-bit key issued by the core backend), event and metric batches are encrypted with AES-256-GCM and POSTed to /api/v1/events/encrypted as {encrypted_payload, batch_id, agent_version, guard_version, guard_core_version}; the wire format is byte-compatible with the Python agent (canonical JSON plaintext with sort_keys and ensure_ascii, 12-byte nonce prefix, 16-byte auth tag, padded urlsafe base64). An invalid key raises EncryptionConfigException at startup; the agent never falls back to plaintext. Signing and compression apply to the envelope body exactly as they do to plaintext batches.

Persistence

With redis configured, every accepted item is written to Redis under a globally-unique key ({prefix}:agent_events:event_<nanos>_<8hex>, TTL 3600s) on enqueue; on start() the buffer reloads whatever a previous process left behind. Every Redis failure is fail-open: logged, counted, and after 3 consecutive write failures paused for a 30s cooldown, so an unhealthy Redis cannot tax the request path. The TTL is the backstop: at worst a lost confirmation duplicates a reload, it never loses data.

Documentation

• AGENTS.md (mirrored byte-identically in CLAUDE.md): architecture, configuration reference, reliability semantics, testing.
• src/.agents/skills/guard-agent-php/SKILL.md: agent-oriented quick reference.

Related projects

• guard-core: the framework-agnostic engine library.
• guard-agent (Python), guardagent (TypeScript), guard-agent-rs (Rust), guard-agent-go (Go): sibling agents.
• guard-core-app: the SaaS platform this agent reports to.

License

MIT. See LICENSE.