added sort comment about php 8 changes

classes/class-get-portfolio.php

@@ -1184,6 +1184,11 @@ private static function get_rand_seed_session() {
 
 	/**
 	 * Sort associative array by custom field.
+	 * In some cases,
+	 * The function may sort elements with the same values ​​differently in php 7 and php 8.
+	 * This is due to the following change in how the usort function works.
+	 * If two members compare as equal, they retain their original order.
+	 * Prior to PHP 8.0.0, their relative order in the sorted array was undefined.
 	 *
 	 * @param array  $array - Sortable array.
 	 * @param string $field - Array field by which sorting will take place.