Make sure that some event subscribers are not executed multiple times

app/Subscriber/BaseSubscriber.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace Kanboard\Subscriber;
+
+use Kanboard\Core\Base;
+
+/**
+ * Base class for subscribers
+ *
+ * @package subscriber
+ * @author  Frederic Guillot
+ */
+class BaseSubscriber extends Base
+{
+    /**
+     * Method called
+     *
+     * @access private
+     * @var array
+     */
+    private $called = array();
+
+    /**
+     * Check if a method has been executed
+     *
+     * @access public
+     * @param  string  $method
+     * @return boolean
+     */
+    public function isExecuted($method = '')
+    {
+        if (isset($this->called[$method])) {
+            return true;
+        }
+
+        $this->called[$method] = true;
+
+        return false;
+    }
+}