Improves readme.

README.md

@@ -1,25 +1,106 @@
 # DD Trace PHP
 
 [![CircleCI](https://circleci.com/gh/DataDog/dd-trace-php/tree/master.svg?style=svg)](https://circleci.com/gh/DataDog/dd-trace-php/tree/master)
+[![OpenTracing Badge](https://img.shields.io/badge/OpenTracing-enabled-blue.svg)](http://opentracing.io)
+[![Minimum PHP Version](https://img.shields.io/badge/php-%3E%3D%205.6-8892BF.svg)](https://php.net/)
 
-PHP APM Client
+Datadog APM client that implements an [OpenTracing](http://opentracing.io) Tracer.
 
-## Install
+## Installation
 
 ```
 composer require datadog/dd-trace
 ```
 
-## Contribution
+## Requirements
 
-### Run tests
+- PHP 5.6 or later
+
+## Usage
+
+In order to be familiar with tracing elements it is recommended to read the [OpenTracing specification](https://github.com/opentracing/specification/blob/master/specification.md).
+
+### Creating a tracer
+
+To start using the Datadog Tracer with the OpenTracing API, you should first initialize the tracer:
+
+```php
+use DDTrace\Encoders\Json;
+use DDTrace\Propagators\TextMap;
+use DDTrace\Tracer;
+use DDTrace\Transport\Http;
+use OpenTracing\Formats;
+
+...
+
+// Transport layer that communicates with the agent
+$transport = new Http(new Json(), $logger, [
+   'endpoint_url' => 'http://localhost:8126/v0.3/traces',
+]);
+
+// Propagation for inject/extract contexts to/from the wire
+$textMap = new TextMap();
+
+// Config for tracer
+$config = [
+    'service_name' => 'my_service',
+    'enabled' => true,
+    'global_tags' => ['host' => 'hostname'],
+];
+
+$tracer = new Tracer($transport, [
+    Formats\TEXT_MAP => $textMap,
+    $config,
+]);
+
+// Sets a global tracer (singleton). Ideally tracer should be
+// injected as a dependency
+GlobalTracer::set($tracer);
+```
+
+### Creating Spans
 
+- [Starting a root span](https://github.com/opentracing/opentracing-php#starting-an-empty-trace-by-creating-a-root-span)
+- [Starting a span for a given request](https://github.com/opentracing/opentracing-php#creating-a-span-given-an-existing-request)
+- [Active span and scope manager](https://github.com/opentracing/opentracing-php#active-spans-and-scope-manager)
+	- [Creating a child span assigning parent manually](https://github.com/opentracing/opentracing-php#creating-a-child-span-assigning-parent-manually)
+	- [Creating a child span using automatic active span management](https://github.com/opentracing/opentracing-php#creating-a-child-span-using-automatic-active-span-management)
+- [Using span options](https://github.com/opentracing/opentracing-php#using-span-options)
+
+### Propagation of context
+
+- [Serializing context to the wire](https://github.com/opentracing/opentracing-php#serializing-to-the-wire)
+- [Deserializing context from the wire](https://github.com/opentracing/opentracing-php#deserializing-from-the-wire)
+- [Propagation formats](https://github.com/opentracing/opentracing-php#propagation-formats)
+
+### Flushing Spans to the agent
+
+PHP as a request scoped language has no simple means to pass the collected spans data to a background process without blocking the main request thread/process. It is mandatory to execute the `Tracer::flush()` after the response is served to the client by using [`register_shutdown_function`](http://php.net/manual/en/function.register-shutdown-function.php).
+
+```php
+use OpenTracing\GlobalTracer;
+
+$application->run();
+
+register_shutdown_function(function() {
+    GlobalTracer::get()->flush();
+});
 ```
+
+## Contributing
+
+### Run tests
+
+```bash
 composer test
 ```
 
 ### Fix lint
 
-```
+```bash
 composer fix-lint
 ```
+
+## Releasing
+
+See [RELEASING](RELEASING.md) for more information on releasing new versions.

RELEASING.md

@@ -0,0 +1,9 @@
+# Releasing DD Trace PHP
+
+## Packagist Package
+
+1. Create a GitHub release.
+
+1. Click `Update` from the admin view of the [datadog/dd-trace][packagist] package.
+
+[packagist]: https://packagist.org/packages/datadog/dd-trace

composer.json

@@ -18,7 +18,6 @@
     "minimum-stability": "dev",
     "require": {
         "php": "^5.6||^7.0",
-        "ext-bcmath": "*",
         "opentracing/opentracing": "1.0.0-beta2",
         "symfony/polyfill": "~1.7.0",
         "guzzlehttp/psr7": "^1.4@dev",
@@ -43,6 +42,9 @@
             "DDTrace\\Tests\\": "./tests/"
         }
     },
+    "provide": {
+        "opentracing/opentracing": "1.0.0-beta2"
+    },
     "scripts": {
         "test": [
             "@test-unit",

src/DDTrace/Encoders/Json.php

@@ -54,14 +54,7 @@ private function encodeSpan(Span $span)
      */
     private function hex2dec($hex)
     {
-        $decimal = 0;
-        $len = strlen($hex);
-
-        for ($i = 1; $i <= $len; $i++) {
-            $decimal = bcadd($decimal, bcmul((string) hexdec($hex[$i - 1]), bcpow('16', (string) ($len - $i))));
-        }
-
-        return $decimal;
+        return base_convert($hex, 16, 10);
     }
 
     /**