Implemented for Sort Processor (work in progress).

src/engine/Api/V1/Processors/Sort.php

@@ -14,7 +14,60 @@
 namespace EA\Engine\Api\V1\Processors; 
 
 class Sort implements ProcessorsInterface {
+    /**
+     * Supports up to 3 fields.
+     * 
+     * @param array &$response The response array to be processed.
+     */
     public static function process(array &$response) {
-        
+        if (!isset($_GET['sort'])) {
+            return; 
+        }
+
+        $sort = explode(',', (string)$_GET['sort']);
+
+        $sortDirection1 = substr($sort[0], 0, 1) === '-' ? SORT_DESC : SORT_ASC; 
+
+        if (isset($sort[1])) {
+            $sortDirection2 = substr($sort[1], 0, 1) === '-' ? SORT_DESC : SORT_ASC; 
+        } else {
+            $sortDirection2 = null; 
+        }
+
+        if (isset($sort[2])) {
+            $sortDirection3 = substr($sort[2], 0, 1) === '-' ? SORT_DESC : SORT_ASC; 
+        } else {
+            $sortDirection3 = null;
+        }
+
+        foreach ($response as $index => $entry) {
+            $sortOrder1[$index] = $entry[substr($sort[0], 1)];
+
+            if ($sortDirection2) {
+                $sortOrder2[$index] = $entry[substr($sort[1], 1)];
+            }
+
+            if ($sortDirection3) {
+                $sortOrder3[$index] = $entry[substr($sort[2], 1)];
+            }
+        }
+
+        $arguments = [
+            $response, 
+            $sortDirection1,
+            $sortOrder1
+        ]; 
+
+        if ($sortDirection2) {
+            $arguments[] = $sortDirection2;
+            $arguments[] = $sortOrder2;
+        }
+
+        if ($sortDirection3) {
+            $arguments[] = $sortDirection3;
+            $arguments[] = $sortOrder3;
+        }
+
+        call_user_func_array('array_multisort', $arguments);        
     }
 }