Description:
------------
substr not truncate UTF-8 correctly, and generate bad UTF-8 string.

test script must be writen in UTF-8

Test script:
---------------
<?php
$str = 'câble TOSLink mâle/mâle (1.5 à 25m)';
$etc = '...';

echo htmlentities(substr($str, 0, 33). $etc, ENT_QUOTES, 'UTF-8')

?>

Expected result:
----------------
câble TOSLink mâle/mâle (1.5 ...

Actual result:
--------------
no return, just PHP error logged: 

PHP Warning:  htmlentities(): Invalid multibyte sequence in argument in C:\DATA\WWW\test.php on line 5

change substr($str, 0, 33) by substr($str, 0, 32), it's work