Auth0 PHP API Integration

Protect PHP API endpoints with JWT access token validation using

auth0/auth0-php

in API mode (

STRATEGY_API

Prerequisites

PHP 8.2+ with extensions:
```
mbstring
```
,
```
openssl
```
,
```
json
```
Composer installed
Auth0 API resource configured (not an Application - must be an API)
If you don't have Auth0 set up yet, use the
```
auth0-quickstart
```
skill first

When NOT to Use

PHP web applications with login/logout flows - Use
```
auth0-php
```
for session-based authentication
Laravel applications - Use
```
auth0/laravel-auth0
```
which has built-in API guard support
Symfony applications - Use
```
auth0/symfony
```
with its security bundle
Single Page Applications - Use
```
auth0-react
```
,
```
auth0-vue
```
, or
```
auth0-angular
```
for client-side auth
Issuing tokens - This skill is for validating access tokens, not issuing them

Quick Start Workflow

1. Install SDK

bash

composer require auth0/auth0-php vlucas/phpdotenv guzzlehttp/guzzle guzzlehttp/psr7 "symfony/cache:^7.0"

```
auth0/auth0-php
```
- The Auth0 SDK (v8.x)
```
vlucas/phpdotenv
```
- Load
```
.env
```
files into
```
$_ENV
```
```
guzzlehttp/guzzle
```
+
```
guzzlehttp/psr7
```
- PSR-18 HTTP client required by the SDK
```
symfony/cache
```
- PSR-6 cache for JWKS key caching (recommended for production)

2. Create Auth0 API

You need an API (not Application) in Auth0.

STOP - ask the user before proceeding.

Ask exactly this question and wait for their answer before doing anything else:
"How would you like to create the Auth0 API resource?
Automated - I'll run Auth0 CLI scripts that create the resource and write the exact values to your
.env
automatically.
Manual - You create the API yourself in the Auth0 Dashboard (or via
auth0 apis create
) and provide me the Domain and Audience.
Which do you prefer? (1 = Automated / 2 = Manual)"
Do NOT proceed to any setup steps until the user has answered. Do NOT default to manual.

If the user chose Automated, follow the Setup Guide for complete CLI scripts. The automated path writes

.env

for you - skip Step 3 below and proceed directly to Step 4.

If the user chose Manual, follow the Setup Guide (Manual Setup section) for full instructions. Then continue with Step 3 below.

Quick reference for manual API creation:

bash

# Using Auth0 CLI
auth0 apis create \
  --name "My PHP API" \
  --identifier https://my-api.example.com \
  --json

Or create manually in Auth0 Dashboard -> Applications -> APIs

3. Configure Environment

Create

.env

bash

AUTH0_DOMAIN=your-tenant.us.auth0.com
AUTH0_AUDIENCE=https://your-api.example.com

AUTH0_DOMAIN

is your Auth0 tenant domain (without

https://

AUTH0_AUDIENCE

is the API identifier you set when creating the API resource in Auth0.

4. Initialize Auth0 in API Mode

Create

auth0.php

to initialize the SDK:

php

<?php

require 'vendor/autoload.php';

use Auth0\SDK\Auth0;
use Auth0\SDK\Configuration\SdkConfiguration;
use Symfony\Component\Cache\Adapter\FilesystemAdapter;

$dotenv = Dotenv\Dotenv::createImmutable(__DIR__);
$dotenv->load();

$configuration = new SdkConfiguration(
    strategy: SdkConfiguration::STRATEGY_API,
    domain: $_ENV['AUTH0_DOMAIN'],
    clientId: null,
    audience: [$_ENV['AUTH0_AUDIENCE']],
    tokenAlgorithm: 'RS256',
    tokenCache: new FilesystemAdapter('auth0_jwks', 600, __DIR__ . '/var/cache'),
    tokenCacheTtl: 600,
);

$auth0 = new Auth0($configuration);

Key differences from web app mode:

```
STRATEGY_API
```
- stateless, no sessions or cookies
```
clientId
```
is not required for RS256 validation (only needed for HS256)
```
audience
```
accepts an array of allowed audience strings
```
tokenCache
```
is a PSR-6
```
CacheItemPoolInterface
```
for JWKS caching

5. Create Middleware Function

Since the SDK does not include a built-in middleware, create a reusable guard function. Create

middleware.php

php

<?php

use Auth0\SDK\Auth0;
use Auth0\SDK\Token;
use Auth0\SDK\Exception\InvalidTokenException;

function requireAuth(Auth0 $auth0, ?array $requiredScopes = null): array
{
    $token = $auth0->getBearerToken(
        server: ['HTTP_AUTHORIZATION']
    );

    if ($token === null) {
        http_response_code(401);
        header('Content-Type: application/json');
        echo json_encode(['error' => 'unauthorized', 'message' => 'Missing or invalid Bearer token']);
        exit;
    }

    $claims = $token->toArray();

    if ($requiredScopes !== null) {
        $grantedScopes = isset($claims['scope']) ? explode(' ', $claims['scope']) : [];
        $missingScopes = array_diff($requiredScopes, $grantedScopes);

        if (!empty($missingScopes)) {
            http_response_code(403);
            header('Content-Type: application/json');
            echo json_encode(['error' => 'insufficient_scope', 'message' => 'Token lacks required scopes']);
            exit;
        }
    }

    return $claims;
}

getBearerToken()

searches for a Bearer token at the locations you specify, verifies the signature against the JWKS endpoint, and validates claims (issuer, audience, expiration). The

server

parameter is an array of

$_SERVER

key names to check (e.g.,

['HTTP_AUTHORIZATION']

) - not

$_SERVER

itself. Returns a

TokenInterface

on success or

null

if no valid token is found (does not throw).

6. Create API Routes

Create

index.php

as a front controller:

php

<?php

require 'auth0.php';
require 'middleware.php';

$method = $_SERVER['REQUEST_METHOD'];
$path = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);

header('Content-Type: application/json');

switch ($path) {
    case '/api/public':
        echo json_encode(['message' => 'Public endpoint - no authentication required']);
        break;

    case '/api/private':
        $claims = requireAuth($auth0);
        echo json_encode(['message' => 'Private endpoint', 'sub' => $claims['sub']]);
        break;

    case '/api/private-scoped':
        $claims = requireAuth($auth0, ['read:messages']);
        echo json_encode(['messages' => [], 'sub' => $claims['sub']]);
        break;

    default:
        http_response_code(404);
        echo json_encode(['error' => 'not_found']);
        break;
}

7. Access Token Claims

The decoded JWT claims are returned as an associative array:

php

$claims = requireAuth($auth0);

$userId = $claims['sub'];       // user/client ID
$scopes = $claims['scope'];     // space-separated granted scopes
$issuer = $claims['iss'];       // issuer (your Auth0 domain URL)
$audience = $claims['aud'];     // audience (string or array)
$expiration = $claims['exp'];   // expiration timestamp

You can also use the

Token

object's typed accessor methods:

php

$token = $auth0->getBearerToken(server: ['HTTP_AUTHORIZATION']);
if ($token !== null) {
    $subject = $token->getSubject();     // returns ?string
    $issuer = $token->getIssuer();       // returns ?string
    $audience = $token->getAudience();   // returns ?array
    $expiration = $token->getExpiration(); // returns ?int
}

8. Add CORS Headers

When your API receives requests from a browser-based SPA, add CORS headers. Create

cors.php

php

<?php

function handleCors(array $allowedOrigins): void
{
    $origin = $_SERVER['HTTP_ORIGIN'] ?? '';

    if (in_array($origin, $allowedOrigins, true)) {
        header("Access-Control-Allow-Origin: $origin");
        header('Access-Control-Allow-Methods: GET, POST, PUT, DELETE, OPTIONS');
        header('Access-Control-Allow-Headers: Authorization, Content-Type');
        header('Access-Control-Max-Age: 86400');
    }

    if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
        http_response_code(204);
        exit;
    }
}

Then add these lines at the top of

index.php

, before the existing

require 'auth0.php'

line:

php

require 'cors.php';
handleCors(['https://your-spa-domain.com']);

The updated

index.php

head should be:

php

<?php

require 'cors.php';
handleCors(['https://your-spa-domain.com']);

require 'auth0.php';
require 'middleware.php';

// ... rest of index.php

CORS must be handled before auth so that preflight

OPTIONS

requests short-circuit without triggering token validation.

9. Test the API

Agent instruction: Start the PHP built-in server and verify the basic endpoints work without credentials:
bash
php -S localhost:8000 index.php &
sleep 1
curl -s http://localhost:8000/api/public
curl -s -o /dev/null -w "%{http_code}" http://localhost:8000/api/private
/api/public
should return
{"message":"Public endpoint - no authentication required"}
/api/private
should return HTTP 401
If both pass, the middleware is working. Kill the background server when done:
bash
kill %1 2>/dev/null
Failcheck: If the server fails to start or
/api/public
errors, check for PHP syntax issues or missing
.env
. After 5-6 failed iterations, use
AskUserQuestion
to ask the user for more details about their environment.

Agent instruction: STOP - ask after basic tests pass.

Once public/401 tests pass, ask the user:

"Your API is set up and the middleware is working (public returns 200, private returns 401 without a token). Would you like me to help you set up testing with a real access token?

Yes - I'll help you configure an M2M application to get test tokens.

No - I'm done for now.

Which do you prefer?"

Do NOT proceed with M2M/token setup unless the user says yes. If they say no, summarize what was done and stop.

Agent instruction (M2M app setup - only if user wants testing):

If the user chose to set up testing, ask:

"To test your protected endpoints, you need a Machine-to-Machine (M2M) application authorized to request tokens for this API.

Create new - I'll create a new M2M application and authorize it for this API.

Use existing - You already have an M2M application. Provide the Client ID and I'll authorize it for this API.

Which do you prefer? (1 = Create new / 2 = Use existing)"

Do NOT proceed until the user answers. Do NOT silently pick an existing application from the tenant.

If the user chose "Create new":
bash
auth0 apps create \
  --name "${PWD##*/} (Test App)" \
  --type m2m \
  --no-input --json
Parse the JSON with
jq
to extract
client_id
. Do NOT use
--reveal-secrets
- never expose client secrets in agent context. Then create a client grant:
bash
auth0 api post "client-grants" --data '{
  "client_id": "<CLIENT_ID>",
  "audience": "<API_IDENTIFIER>",
  "scope": ["<SCOPES>"]
}'
If the user chose "Use existing": Ask for the Client ID. Then create a client grant to authorize it for this API:
bash
auth0 api post "client-grants" --data '{
  "client_id": "<USER_PROVIDED_CLIENT_ID>",
  "audience": "<API_IDENTIFIER>",
  "scope": ["<SCOPES>"]
}'
If the grant already exists (409 conflict), that's fine - the app is already authorized.

Agent instruction (TOKEN ISOLATION - CRITICAL):

The agent MUST NEVER directly see or display access token values. Token security rules:
Do NOT run
auth0 test token
on its own - it outputs the token to stdout
Do NOT ask the user to paste their token into the conversation

Do NOT echo, print, or log the token value

Do NOT store the token in a file
Secure testing approach (single-command chain):

If the user explicitly asks to test the protected endpoints, use a single-command chain that captures the token into a shell variable and immediately uses it:
bash
php -S localhost:8000 index.php &
sleep 1
TEST_TOKEN=$(auth0 test token <M2M_CLIENT_ID> --audience <AUDIENCE> --scopes <SCOPE1,SCOPE2> 2>/dev/null | grep -o 'ey[A-Za-z0-9_-]*\.[A-Za-z0-9_-]*\.[A-Za-z0-9_-]*') && \
[ -n "$TEST_TOKEN" ] && echo "Token acquired (${#TEST_TOKEN} chars)" && \
echo "=== GET /api/private ===" && \
curl -s http://localhost:8000/api/private -H "Authorization: Bearer $TEST_TOKEN" && \
echo "" && echo "=== GET /api/private-scoped ===" && \
curl -s http://localhost:8000/api/private-scoped -H "Authorization: Bearer $TEST_TOKEN"
kill %1 2>/dev/null
Rules:
ONLY use when the user explicitly asks to test
Always chain token acquisition + curl in a SINGLE
&&
command
NEVER add
echo $TEST_TOKEN
or any command that would print the raw token value
If the token acquisition fails (empty variable), report that the M2M app may not be authorized

Client ID is REQUIRED - if M2M setup was not completed, ask the user first
If the user does NOT ask to test, just provide the commands for them to run manually:
auth0 test token <CLIENT_ID> --audience <AUDIENCE> --scopes <SCOPE1,SCOPE2>
curl http://localhost:8000/api/private -H "Authorization: Bearer <PASTE_TOKEN_HERE>"

Start the server:

bash

php -S localhost:8000 index.php

Test public endpoint (no token needed):

bash

curl http://localhost:8000/api/public

Test protected endpoint without token (should return 401):

bash

curl http://localhost:8000/api/private

Test protected endpoint with token:

bash

curl http://localhost:8000/api/private \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN"

Test scoped endpoint:

bash

curl http://localhost:8000/api/private-scoped \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN"

Get a test token via Auth0 Dashboard -> APIs -> Test tab, or via the M2M flow described above.

Common Mistakes

Mistake	Fix
Hardcoding `domain` or `audience` in source	Always read from environment variables - never embed credentials in code
Using `STRATEGY_REGULAR` for an API	API mode must use `SdkConfiguration::STRATEGY_API` - it disables sessions and cookies
Installing without a PSR-18 HTTP client	Must have `guzzlehttp/guzzle` or another PSR-18 client or the SDK cannot fetch JWKS
Not caching JWKS keys	Without a PSR-6 cache, the SDK fetches JWKS on every request - always configure `tokenCache`
Passing `audience` as a string	`audience` must be an array: `['https://my-api.example.com']` not `'https://my-api.example.com'`
Passing `domain` as full URL with `https://`	`domain` should be the bare domain, e.g. `my-tenant.us.auth0.com` , not `https://my-tenant.us.auth0.com`
Using `decode()` without specifying token type	Always pass `tokenType: Token::TYPE_ACCESS_TOKEN` when manually calling `decode()`
Echoing exception messages to users	Use `error_log()` for the real error and return a generic JSON error message
Using an ID token instead of an access token	Must use the access token for API auth - ID tokens are for the client app
Created an Application instead of an API in Auth0	Must create an API resource (Applications -> APIs) - an Application doesn't issue access tokens with the right audience
Setting `clientId` and expecting RS256 to need it	For RS256, `clientId` is optional - the SDK validates against the JWKS endpoint
Using `clientSecret` for RS256 validation	`clientSecret` is only needed for HS256 - RS256 uses the public key from JWKS
Passing `$_SERVER` directly to `getBearerToken()`	The `server` param takes an array of key names to look up, e.g. `['HTTP_AUTHORIZATION']` - not `$_SERVER` itself

Key SDK Methods

Method	Returns	Purpose
`getBearerToken`	`?TokenInterface`	Searches specified `$_SERVER` keys for a Bearer token, verifies signature, validates claims. Returns `null` if no token found or validation fails (does not throw).
`decode`	`TokenInterface`	Manually decodes and validates a JWT string
`configuration`	`SdkConfiguration`	Access the SDK configuration instance
`Token::toArray`	`array`	Returns all token claims as an associative array
`Token::getSubject`	`?string`	Returns the `sub` claim (user/client ID)
`Token::getIssuer`	`?string`	Returns the `iss` claim
`Token::getAudience`	`?array`	Returns the `aud` claim
`Token::getExpiration`	`?int`	Returns the `exp` claim (Unix timestamp)

Related Skills

```
auth0-php
```
- For PHP web apps with login/logout using session-based auth
```
auth0-quickstart
```
- Basic Auth0 setup and framework detection
```
auth0-cli
```
- Manage Auth0 resources from the terminal
```
auth0-mfa
```
- Add Multi-Factor Authentication

Quick Reference

SdkConfiguration for APIs:

php

$configuration = new SdkConfiguration(
    strategy: SdkConfiguration::STRATEGY_API,       // required - stateless mode
    domain: $_ENV['AUTH0_DOMAIN'],                   // required
    audience: [$_ENV['AUTH0_AUDIENCE']],             // required - array of identifiers
    tokenAlgorithm: 'RS256',                        // default
    tokenCache: $psrCacheAdapter,                    // recommended for production
    tokenCacheTtl: 600,                             // JWKS cache TTL in seconds
);

Token validation:

php

$token = $auth0->getBearerToken(server: ['HTTP_AUTHORIZATION']);  // returns ?TokenInterface
$claims = $token->toArray();                         // all claims as array
$userId = $token->getSubject();                      // sub claim

Manual decode:

php

use Auth0\SDK\Token;

$token = $auth0->decode(
    $jwtString,
    tokenType: Token::TYPE_ACCESS_TOKEN,
);

Environment variables:

```
AUTH0_DOMAIN
```
- your Auth0 tenant domain (e.g.
```
tenant.us.auth0.com
```
)
```
AUTH0_AUDIENCE
```
- your API identifier (e.g.
```
https://api.example.com
```
)

Common Use Cases:

Protect routes ->
```
requireAuth($auth0)
```
(see Step 5)
Scope enforcement ->
```
requireAuth($auth0, ['read:messages'])
```
(see Step 5)
CORS setup -> Integration Guide
Multi-audience validation -> Integration Guide
Advanced configuration -> API Reference

Detailed Documentation

Setup Guide - Auth0 CLI setup, environment configuration, getting test tokens
Integration Guide - Scopes, permissions, middleware, multi-audience, CORS, error handling
API Reference - Complete SDK API for API mode, configuration options, token methods

auth0-php-api

NPX Install

Tags

SKILL.md Content

Auth0 PHP API Integration

Prerequisites

When NOT to Use

Quick Start Workflow

1. Install SDK

2. Create Auth0 API

3. Configure Environment

4. Initialize Auth0 in API Mode

5. Create Middleware Function

6. Create API Routes

7. Access Token Claims

8. Add CORS Headers

9. Test the API

Common Mistakes

Key SDK Methods

Related Skills

Quick Reference

Detailed Documentation

References