Prepping everything for a PHP 8 release

src/EntityCollection.php

@@ -308,6 +308,12 @@ class EntityCollection extends \ArrayObject {
             $this->append( $this->arrayToEntity($value) );
         }
         else {
+            foreach ($this as $duplicate) {
+                if ($duplicate === $value) {
+                    return;
+                }
+            }
+
             parent::append($value);
         }
     }