# Authentication (PHP SDK)

The Market Data PHP SDK requires an API token to authenticate requests. You can obtain a token from the [Market Data Dashboard](https://www.marketdata.app/dashboard/).

## Token Configuration

The SDK supports multiple methods for providing your API token, with the following priority order (highest to lowest):

1. **Explicit token parameter** - Passed directly to the Client constructor
2. **Environment variable** - `MARKETDATA_TOKEN`
3. **.env file** - Using phpdotenv
4. **Empty string** - For accessing free endpoints only

### Setting the Environment Variable

### Mac/Linux

Add to your shell profile (`.bashrc`, `.zshrc`, etc.):

```bash
export MARKETDATA_TOKEN="your_api_token_here"
```

Then reload your shell:

```bash
source ~/.bashrc  # or source ~/.zshrc
```

### Windows

Using Command Prompt:

```batch
setx MARKETDATA_TOKEN "your_api_token_here"
```

Using PowerShell:

```powershell
[Environment]::SetEnvironmentVariable("MARKETDATA_TOKEN", "your_api_token_here", "User")
```

### Using a .env File

Create a `.env` file in your project root:

```ini
MARKETDATA_TOKEN=your_api_token_here
```

The SDK automatically loads `.env` files using phpdotenv.

### Explicit Token Parameter

Pass the token directly to the Client constructor:

```php
<?php

use MarketDataApp\Client;

$client = new Client('your_api_token_here');
```

## Token Validation

The SDK validates your token during client initialization by making a request to the `/user/` endpoint. If the token is invalid, an `UnauthorizedException` is thrown:

```php
<?php

use MarketDataApp\Client;
use MarketDataApp\Exceptions\UnauthorizedException;

try {
    $client = new Client('invalid_token');
} catch (UnauthorizedException $e) {
    echo "Invalid API token: " . $e->getMessage();
}
```

## Testing Your Token

Verify your token is working correctly:

```php
<?php

require_once 'vendor/autoload.php';

use MarketDataApp\Client;

$client = new Client();

// Get rate limit information
$user = $client->utilities->user();

echo "Requests Used Today: " . $user->requests_made_today . "\n";
echo "Daily Request Limit: " . $user->daily_requests . "\n";
echo "Requests Remaining: " . ($user->daily_requests - $user->requests_made_today) . "\n";
```

## Security Best Practices

- **Never commit your API token** to version control
- Add `.env` to your `.gitignore` file
- Use environment variables in production environments
- Rotate tokens regularly if compromised

## Next Steps

After configuring authentication, learn about the [Client](https://www.marketdata.app/docs/sdk/php/client) class to start making API requests.