Document binding tags (giveTags)

Author: simensen

container.md

@@ -9,6 +9,7 @@
     - [Binding Typed Variadics](#binding-typed-variadics)
     - [Tagging](#tagging)
     - [Extending Bindings](#extending-bindings)
+    - [Binding Tags](#binding-tags)
 - [Resolving](#resolving)
     - [The Make Method](#the-make-method)
     - [Automatic Injection](#automatic-injection)
@@ -221,6 +222,46 @@ Once the services have been tagged, you may easily resolve them all via the `tag
         return new ReportAggregator($app->tagged('reports'));
     });
 
+
+<a name="binding-tags"></a>
+### Binding Tags
+
+If a class needs an array of instances or a variadic constructor argument, you can instruct the container to resolve that dependency with tagged services.
+
+To bind services tagged as "reports" to a primitive (`array`) constructor argument named `$reports`:
+
+    class ReportAggregator
+    {
+        /** @var Report[] */
+        public $reports;
+
+        public function __construct(array $reports)
+        {
+            $this->reports = $reports;
+        }
+    }
+
+    $this->app->when(ReportAggregator::class)
+        ->needs('$reports')
+        ->giveTagged('reports');
+
+To bind services tagged as "reports" to a variadic constructor argument typed `Report`:
+
+    class ReportAggregator
+    {
+        /** @var Report[] */
+        public $reports;
+
+        public function __construct(Report ...$reports)
+        {
+            $this->reports = $reports;
+        }
+    }
+
+    $this->app->when(ReportAggregator::class)
+        ->needs(Report::class)
+        ->giveTagged('reports');
+
 <a name="extending-bindings"></a>
 ### Extending Bindings