diff --git a/.github/workflows/e2e-tests.yml b/.github/workflows/e2e-tests.yml
new file mode 100644
index 0000000..9dca93b
--- /dev/null
+++ b/.github/workflows/e2e-tests.yml
@@ -0,0 +1,58 @@
+name: E2E Tests
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+  workflow_dispatch:
+    inputs:
+      e2e_tests_ref:
+        description: 'Branch or ref of sdk-e2e-tests to use'
+        required: false
+        default: 'main'
+
+jobs:
+  e2e-tests:
+    if: ${{ github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository }}
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout SDK
+        uses: actions/checkout@v4
+        with:
+          path: sdk
+
+      - name: Checkout sdk-e2e-tests
+        uses: actions/checkout@v4
+        with:
+          repository: segmentio/sdk-e2e-tests
+          ref: ${{ inputs.e2e_tests_ref || 'main' }}
+          token: ${{ secrets.E2E_TESTS_TOKEN }}
+          path: sdk-e2e-tests
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.2'
+          extensions: curl, json
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Run E2E tests
+        working-directory: sdk-e2e-tests
+        run: |
+          ./scripts/run-tests.sh \
+            --sdk-dir "${{ github.workspace }}/sdk/e2e-cli" \
+            --cli "php ${{ github.workspace }}/sdk/e2e-cli/main.php"
+
+      - name: Upload test results
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: e2e-test-results
+          path: sdk-e2e-tests/test-results/
+          if-no-files-found: ignore
diff --git a/.github/workflows/publish-e2e-cli.yml b/.github/workflows/publish-e2e-cli.yml
new file mode 100644
index 0000000..ec647f0
--- /dev/null
+++ b/.github/workflows/publish-e2e-cli.yml
@@ -0,0 +1,39 @@
+name: Publish E2E CLI
+
+on:
+  push:
+    branches: [master]
+    paths:
+      - 'e2e-cli/**'
+      - 'lib/**'
+  schedule:
+    - cron: '0 0 1 * *'
+  workflow_dispatch:
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout SDK
+        uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.2'
+          extensions: curl, json
+
+      - name: Prepare artifact
+        run: |
+          mkdir -p artifact
+          cp e2e-cli/main.php artifact/
+          cp e2e-cli/e2e-config.json artifact/
+          cp e2e-cli/run-e2e.sh artifact/
+          cp -r lib artifact/lib
+
+      - name: Upload CLI artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: e2e-cli-php
+          path: artifact/
+          retention-days: 90
diff --git a/e2e-cli/README.md b/e2e-cli/README.md
new file mode 100644
index 0000000..4126b08
--- /dev/null
+++ b/e2e-cli/README.md
@@ -0,0 +1,131 @@
+# analytics-php e2e-cli
+
+A small CLI tool that drives the analytics-php SDK in end-to-end tests.
+
+## Requirements
+
+- PHP 7.4 or 8.x
+
+No `composer install` is required — `main.php` uses a simple `spl_autoload_register`
+to load the SDK classes directly from `../lib/`.
+
+## Usage
+
+```bash
+php main.php --input '<json>'
+```
+
+### Input JSON format
+
+```json
+{
+  "writeKey": "YOUR_WRITE_KEY",
+  "apiHost": "https://api.segment.io",
+  "sequences": [
+    {
+      "delayMs": 0,
+      "events": [
+        {
+          "type": "track",
+          "event": "Test Event",
+          "userId": "user-1",
+          "properties": { "plan": "pro" }
+        },
+        {
+          "type": "identify",
+          "userId": "user-1",
+          "traits": { "email": "user@example.com" }
+        },
+        {
+          "type": "page",
+          "userId": "user-1",
+          "name": "Home",
+          "category": "Nav"
+        },
+        {
+          "type": "screen",
+          "userId": "user-1",
+          "name": "Main Screen"
+        },
+        {
+          "type": "alias",
+          "userId": "new-id",
+          "previousId": "old-id"
+        },
+        {
+          "type": "group",
+          "userId": "user-1",
+          "groupId": "group-1",
+          "traits": { "name": "Acme Corp" }
+        }
+      ]
+    }
+  ],
+  "config": {
+    "flushAt": 15,
+    "timeout": 10
+  }
+}
+```
+
+| Field | Description |
+|---|---|
+| `writeKey` | Segment write key |
+| `apiHost` | Full URL of the Segment API host (scheme is stripped; PHP SDK always uses HTTPS) |
+| `sequences[].delayMs` | Milliseconds to wait before processing this sequence |
+| `sequences[].events` | List of events to send |
+| `config.flushAt` | Number of events to accumulate before auto-flushing (maps to `flush_at`) |
+| `config.timeout` | cURL timeout in seconds (maps to `curl_timeout`) |
+
+### Supported event types
+
+`track`, `identify`, `page`, `screen`, `alias`, `group`
+
+### Output JSON (stdout)
+
+On success:
+
+```json
+{"success": true, "sentBatches": 1}
+```
+
+On failure:
+
+```json
+{"success": false, "sentBatches": 0, "error": "HTTP 400: Bad Request"}
+```
+
+Exit code is `0` on success and `1` on failure. Debug logs are written to **stderr**.
+
+## Running E2E tests
+
+```bash
+./run-e2e.sh
+```
+
+By default this expects the `sdk-e2e-tests` repo to be checked out alongside
+the `analytics-php` repo:
+
+```
+parent/
+  analytics-php/
+    e2e-cli/         ← you are here
+  sdk-e2e-tests/
+```
+
+Override the location with an environment variable:
+
+```bash
+E2E_TESTS_DIR=/path/to/sdk-e2e-tests ./run-e2e.sh
+```
+
+Any additional arguments are forwarded to `sdk-e2e-tests/scripts/run-tests.sh`.
+
+## How it works
+
+1. `main.php` parses `--input` JSON from `$argv`.
+2. A `Segment\Client` is created with `lib_curl` consumer and the provided options.
+3. Each sequence is processed in order; `delayMs` introduces an optional pause.
+4. After all events are enqueued, `flush()` is called to send them synchronously.
+5. Errors captured by the `error_handler` callback or a `false` return from
+   `flush()` cause the script to exit with code `1`.
diff --git a/e2e-cli/composer.json b/e2e-cli/composer.json
new file mode 100644
index 0000000..cea3b6f
--- /dev/null
+++ b/e2e-cli/composer.json
@@ -0,0 +1,13 @@
+{
+  "name": "segment/analytics-php-e2e-cli",
+  "description": "E2E testing CLI for Segment Analytics PHP",
+  "type": "project",
+  "require": {
+    "php": "^7.4 || ^8.0"
+  },
+  "autoload": {
+    "psr-4": {
+      "Segment\\": "../lib/"
+    }
+  }
+}
diff --git a/e2e-cli/e2e-config.json b/e2e-cli/e2e-config.json
new file mode 100644
index 0000000..071d5fc
--- /dev/null
+++ b/e2e-cli/e2e-config.json
@@ -0,0 +1,7 @@
+{
+  "sdk": "php",
+  "test_suites": "basic",
+  "auto_settings": false,
+  "patch": null,
+  "env": {}
+}
diff --git a/e2e-cli/main.php b/e2e-cli/main.php
new file mode 100644
index 0000000..4695981
--- /dev/null
+++ b/e2e-cli/main.php
@@ -0,0 +1,319 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * E2E CLI for analytics-php
+ *
+ * Usage:
+ *   php main.php --input '<json>'
+ *
+ * Input JSON format:
+ * {
+ *   "writeKey": "...",
+ *   "apiHost": "https://...",
+ *   "sequences": [
+ *     {
+ *       "delayMs": 0,
+ *       "events": [
+ *         {"type": "track", "event": "Test", "userId": "user-1", "properties": {...}},
+ *         ...
+ *       ]
+ *     }
+ *   ],
+ *   "config": {
+ *     "flushAt": 15,
+ *     "timeout": 10
+ *   }
+ * }
+ *
+ * Output JSON to stdout:
+ *   {"success": true, "sentBatches": 1}
+ *   {"success": false, "sentBatches": 0, "error": "..."}
+ *
+ * Exit code: 0 on success, 1 on failure.
+ */
+
+// Autoload the Segment SDK from the parent lib/ directory.
+spl_autoload_register(function (string $class): void {
+    $prefix = 'Segment\\';
+    $baseDir = __DIR__ . '/../lib/';
+
+    if (strncmp($prefix, $class, strlen($prefix)) !== 0) {
+        return;
+    }
+
+    $relative = substr($class, strlen($prefix));
+    $file = $baseDir . str_replace('\\', '/', $relative) . '.php';
+
+    if (file_exists($file)) {
+        require $file;
+    }
+});
+
+/**
+ * LibCurl subclass that allows overriding the protocol (http:// vs https://).
+ * The base class hardcodes $protocol = 'https://', so we extend it to support
+ * plain-HTTP targets used by the mock test server.
+ */
+class E2eLibCurl extends \Segment\Consumer\LibCurl
+{
+    public function __construct(string $secret, array $options = [])
+    {
+        parent::__construct($secret, $options);
+        if (isset($options['protocol'])) {
+            $this->protocol = $options['protocol'];
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+function debugLog(string $msg): void
+{
+    fwrite(STDERR, '[e2e-cli] ' . $msg . PHP_EOL);
+}
+
+function outputResult(bool $success, int $sentBatches, string $error = ''): void
+{
+    $result = [
+        'success'     => $success,
+        'sentBatches' => $sentBatches,
+    ];
+    if (!$success && $error !== '') {
+        $result['error'] = $error;
+    }
+    echo json_encode($result) . PHP_EOL;
+}
+
+/**
+ * Parse the --input argument from $argv.
+ *
+ * @param array<int,string> $argv
+ * @return string|null
+ */
+function parseInputArg(array $argv): ?string
+{
+    for ($i = 1, $iMax = count($argv); $i < $iMax; $i++) {
+        if ($argv[$i] === '--input' && isset($argv[$i + 1])) {
+            return $argv[$i + 1];
+        }
+        if (strncmp($argv[$i], '--input=', 8) === 0) {
+            return substr($argv[$i], 8);
+        }
+    }
+    return null;
+}
+
+/**
+ * Given a full URL like "https://api.segment.io" or "http://localhost:8080",
+ * return just the host[:port] portion that the PHP SDK expects.
+ *
+ * The PHP SDK prepends "https://" itself (hardcoded in QueueConsumer), so we
+ * strip the scheme here and only keep host + optional port.
+ *
+ * @param string $apiHost
+ * @return string
+ */
+function parseHost(string $apiHost): string
+{
+    // Remove trailing slash
+    $apiHost = rtrim($apiHost, '/');
+
+    // Strip scheme
+    $apiHost = preg_replace('#^https?://#', '', $apiHost);
+
+    // Remove any path component — keep only host[:port]
+    $parts = explode('/', $apiHost, 2);
+
+    return $parts[0];
+}
+
+/**
+ * Build the options array for Segment\Client.
+ *
+ * @param array<string,mixed>   $input
+ * @param array<int,string>    &$errors   collected error messages
+ * @return array<string,mixed>
+ */
+function buildClientOptions(array $input, array &$errors): array
+{
+    $config  = $input['config'] ?? [];
+    $apiHost = $input['apiHost'] ?? '';
+
+    // Determine protocol from the apiHost scheme (default https://).
+    $scheme = 'https://';
+    if (preg_match('#^(https?)://#i', $apiHost, $m)) {
+        $scheme = strtolower($m[1]) . '://';
+    }
+
+    $options = [
+        // Use our subclass so we can inject a plain-http:// protocol for the
+        // mock test server (the base LibCurl hardcodes https://).
+        'consumer'      => E2eLibCurl::class,
+        'protocol'      => $scheme,
+        'error_handler' => function (int $code, string $message) use (&$errors): void {
+            $msg = "HTTP {$code}: {$message}";
+            debugLog('SDK error — ' . $msg);
+            $errors[] = $msg;
+        },
+    ];
+
+    if ($apiHost !== '') {
+        $options['host'] = parseHost($apiHost);
+        debugLog('Using host: ' . $options['host'] . ' (protocol: ' . $scheme . ')');
+    }
+
+    if (isset($config['flushAt']) && is_numeric($config['flushAt'])) {
+        $options['flush_at'] = (int)$config['flushAt'];
+        debugLog('flush_at: ' . $options['flush_at']);
+    }
+
+    if (isset($config['timeout']) && is_numeric($config['timeout'])) {
+        $options['curl_timeout'] = (int)$config['timeout'];
+        debugLog('curl_timeout: ' . $options['curl_timeout']);
+    }
+
+    return $options;
+}
+
+/**
+ * Map an event array from the input JSON to the array accepted by the SDK.
+ * Only passes fields that are set in the input event.
+ *
+ * @param array<string,mixed> $event
+ * @return array<string,mixed>
+ */
+function buildMessage(array $event): array
+{
+    $fieldMap = [
+        'userId',
+        'anonymousId',
+        'messageId',
+        'timestamp',
+        'traits',
+        'properties',
+        'name',
+        'category',
+        'groupId',
+        'previousId',
+        'context',
+        'integrations',
+        'event',
+    ];
+
+    $message = [];
+    foreach ($fieldMap as $field) {
+        if (array_key_exists($field, $event)) {
+            $message[$field] = $event[$field];
+        }
+    }
+
+    return $message;
+}
+
+// ---------------------------------------------------------------------------
+// Main
+// ---------------------------------------------------------------------------
+
+$inputJson = parseInputArg($argv);
+
+if ($inputJson === null) {
+    outputResult(false, 0, 'Missing required --input argument');
+    exit(1);
+}
+
+$input = json_decode($inputJson, true);
+
+if (!is_array($input)) {
+    outputResult(false, 0, 'Failed to parse --input JSON: ' . json_last_error_msg());
+    exit(1);
+}
+
+$writeKey  = $input['writeKey']  ?? '';
+$sequences = $input['sequences'] ?? [];
+
+if ($writeKey === '') {
+    outputResult(false, 0, 'Missing writeKey in input');
+    exit(1);
+}
+
+$errors = [];
+
+// Build client options (error_handler captures into $errors by reference)
+$options = buildClientOptions($input, $errors);
+
+debugLog('Creating Segment\\Client with writeKey=' . substr($writeKey, 0, 4) . '...');
+
+$client = new \Segment\Client($writeKey, $options);
+
+$sentBatches = 0;
+
+foreach ($sequences as $seqIndex => $sequence) {
+    $delayMs = (int)($sequence['delayMs'] ?? 0);
+
+    if ($delayMs > 0) {
+        debugLog("Sequence {$seqIndex}: sleeping {$delayMs}ms");
+        usleep($delayMs * 1000);
+    }
+
+    $events = $sequence['events'] ?? [];
+    debugLog("Sequence {$seqIndex}: processing " . count($events) . ' event(s)');
+
+    foreach ($events as $eventIndex => $event) {
+        $type    = $event['type'] ?? '';
+        $message = buildMessage($event);
+
+        debugLog("  [{$seqIndex}/{$eventIndex}] Enqueueing {$type}");
+
+        switch ($type) {
+            case 'track':
+                $client->track($message);
+                break;
+            case 'identify':
+                $client->identify($message);
+                break;
+            case 'page':
+                $client->page($message);
+                break;
+            case 'screen':
+                $client->screen($message);
+                break;
+            case 'alias':
+                $client->alias($message);
+                break;
+            case 'group':
+                $client->group($message);
+                break;
+            default:
+                $errors[] = "Unknown event type: {$type}";
+                debugLog("  Unknown event type: {$type}");
+                break;
+        }
+    }
+}
+
+debugLog('Flushing...');
+$flushOk = $client->flush();
+
+if ($flushOk) {
+    $sentBatches = 1;
+    debugLog('Flush succeeded');
+} else {
+    debugLog('Flush returned false');
+    $errors[] = 'Flush failed';
+}
+
+$hasErrors = !empty($errors);
+$success   = $flushOk && !$hasErrors;
+
+if ($success) {
+    outputResult(true, $sentBatches);
+    exit(0);
+} else {
+    $errorMsg = implode('; ', $errors);
+    outputResult(false, $sentBatches, $errorMsg);
+    exit(1);
+}
diff --git a/e2e-cli/run-e2e.sh b/e2e-cli/run-e2e.sh
new file mode 100755
index 0000000..43afd98
--- /dev/null
+++ b/e2e-cli/run-e2e.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+#
+# Run E2E tests for analytics-php
+#
+# Prerequisites: Node.js 18+ and PHP 7.4+
+#
+# Usage:
+#   ./run-e2e.sh [extra args passed to run-tests.sh]
+#
+# Override sdk-e2e-tests location:
+#   E2E_TESTS_DIR=../my-e2e-tests ./run-e2e.sh
+#
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SDK_ROOT="$SCRIPT_DIR/.."
+E2E_DIR="${E2E_TESTS_DIR:-$SDK_ROOT/../sdk-e2e-tests}"
+
+echo "=== Building analytics-php e2e-cli ==="
+
+# Run tests
+cd "$E2E_DIR"
+./scripts/run-tests.sh \
+    --sdk-dir "$SCRIPT_DIR" \
+    --cli "php $SCRIPT_DIR/main.php" \
+    "$@"