Improve UtfString handling of invalid strings

First check whether string is actually utf-8 before trying to process it
as it.

Fixes https://github.com/phpmyadmin/phpmyadmin/issues/13385

Signed-off-by: Michal Čihař <michal@cihar.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/UtfString.php b/src/UtfString.php
index e3dc512..0d2e0c5 100644
--- a/src/UtfString.php
+++ b/src/UtfString.php
@@ -75,7 +75,11 @@ class UtfString implements \ArrayAccess
         $this->byteIdx = 0;
         $this->charIdx = 0;
         $this->byteLen = mb_strlen($str, '8bit');
-        $this->charLen = mb_strlen($str, 'UTF-8');
+        if (! mb_check_encoding($str, 'UTF-8')) {
+            $this->charLen = 0;
+        } else {
+            $this->charLen = mb_strlen($str, 'UTF-8');
+        }
     }
 
     /**