Fix examples/traces/demo (#755)

Author: Nevay

examples/traces/demo/docker-compose.yml

@@ -4,7 +4,7 @@ x-otel-common:
   OTEL_TRACES_SAMPLER: parentbased_always_on
   OTEL_TRACES_EXPORTER: otlp
   OTEL_EXPORTER_OTLP_TRACES_PROTOCOL: grpc
-  OTEL_EXPORTER_OTLP_ENDPOINT: localhost:4317
+  OTEL_EXPORTER_OTLP_ENDPOINT: collector:4317
   OTEL_PHP_TRACES_PROCESSOR: simple
 
 version: '3.7'

examples/traces/demo/src/index.php

@@ -14,16 +14,15 @@
 use OpenTelemetry\API\Trace\StatusCode;
 use OpenTelemetry\Context\Context;
 use OpenTelemetry\SDK\Trace\Tracer;
-use OpenTelemetry\SDK\Trace\TracerProvider;
 use OpenTelemetry\SDK\Trace\TracerProviderFactory;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface as Response;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Psr\Http\Server\RequestHandlerInterface as RequestHandler;
 use Slim\Routing\RouteContext;
 
-//create default tracer from environment variables, now available as TracerProvider::getDefaultTracer
-$tracer = (new TracerProviderFactory('example'))->create()->getTracer('io.opentelemetry.contrib.php');
+$tracerProvider = (new TracerProviderFactory('example'))->create();
+$tracer = $tracerProvider->getTracer('io.opentelemetry.contrib.php');
 
 $cb = new ContainerBuilder();
 $container = $cb->addDefinitions([