Merge pull request #4815 from aydreeihn/issue/mpdf-phpversion

Issue: MPDF Export PHP < 7.0

bootstrap.php

@@ -295,6 +295,12 @@ class Bootstrap {
         if (extension_loaded('iconv'))
             iconv_set_encoding('internal_encoding', 'UTF-8');
 
+        if (intval(phpversion()) < 7) {
+            function random_int($a, $b) {
+                return rand($a, $b);
+            }
+        }
+
         function mb_str_wc($str) {
             return count(preg_split('~[^\p{L}\p{N}\'].+~u', trim($str)));
         }