API-410: Add doc for php client about creating family variant

Author: Willy

content/php-client/resources/family-variants.md

@@ -30,3 +30,29 @@ $client = new \Akeneo\Pim\AkeneoPimClientBuilder('http://akeneo.com/')->buildAut
  */
 $familyVariant = $client->getFamilyVariantApi()->get('boots', 'boots_color_size');
 ```
+
+### Create a family variant
+
+If the family variant does not exist yet, this method creates it, otherwise it throws an exception.
+
+```php
+$client = new \Akeneo\Pim\AkeneoPimClientBuilder('http://akeneo.com/')->buildAuthenticatedByPassword('client_id', 'secret', 'admin', 'admin');
+
+$client->getFamilyVariantApi()->create('boots', 'boots_size_color', [
+    'labels' => [
+        'en_US' => 'Boots by color and size'
+    ],
+    'variant_attribute_sets' => [
+        [
+            'level' => 1,
+            'axes' => ['size'],
+            'attributes' => ['name', 'description', 'size']
+        ],
+        [
+            'level' => 2,
+            'axes' => ['color'],
+            'attributes' => ['sku', 'color']
+        ]
+    ]
+]);
+```