add-basic-graphql-functionality (#27)

Author: Busfox

README.md

@@ -79,6 +79,40 @@ $service = new Shopify\Service\ProductService($client);
 $service->delete($productId);
 ```
 
+### GraphQL
+
+#### Query
+```php
+$service = new Shopify\Service\GraphQLService($client);
+$service->graph(
+  '{
+    products(query: "created_at:<2019", first: 5) {
+      edges {
+        node {
+          title
+          description
+        }
+      }
+    }
+  }'
+);
+```
+
+#### Mutation
+```php
+$service = new Shopify\Service\GraphQLService($client);
+$service->graph(
+  'mutation productCreate($input: ProductInput!){
+    productCreate(input: $input) {
+      product {
+        id
+      }
+    }
+  }',
+  ['input' => ['title' => 'Sweet new product','productType' => 'Snowboard','vendor' => 'JadedPixel']]
+);
+```
+
 ## Authentication
 
 Authentication to Shopify's API is done through access tokens, which are obtained through OAuth. To get a

lib/Service/GraphQLService.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace Shopify\Service;
+
+class GraphQLService extends AbstractService
+{
+
+  public function graph(string $query, array $variables = [])
+  {
+    // Build the request
+    $request = ['query' => $query];
+    if (count($variables) > 0) {
+        $request['variables'] = $variables;
+    }
+
+    // Create the request, pass the access token and optional parameters
+    $endpoint = '/admin/api/graphql.json';
+    $response = $this->request(
+        $endpoint,
+        'POST',
+        $request
+    );
+
+    return (object) [
+        'response'   => $response
+    ];
+  }
+}