Replace non multibyte-safe functions with corresponding mb function.
Risky when any of the functions are overridden, or when relying on the string byte size rather than its length in characters.
--- Original
+++ New
<?php
-$a = strlen($a);
-$a = strpos($a, $b);
-$a = strrpos($a, $b);
-$a = substr($a, $b);
-$a = strtolower($a);
-$a = strtoupper($a);
-$a = stripos($a, $b);
-$a = strripos($a, $b);
-$a = strstr($a, $b);
-$a = stristr($a, $b);
-$a = strrchr($a, $b);
-$a = substr_count($a, $b);
+$a = mb_strlen($a);
+$a = mb_strpos($a, $b);
+$a = mb_strrpos($a, $b);
+$a = mb_substr($a, $b);
+$a = mb_strtolower($a);
+$a = mb_strtoupper($a);
+$a = mb_stripos($a, $b);
+$a = mb_strripos($a, $b);
+$a = mb_strstr($a, $b);
+$a = mb_stristr($a, $b);
+$a = mb_strrchr($a, $b);
+$a = mb_substr_count($a, $b);