Usage of strlen(tuf8_decode()) and "/u" regex modifier

Hello, As indicated below, the "strlen(tuf8_decode())" and the "/u" regex modifier do not work as per my understanding. 1) What is my misunderstanding? <?php $the_string = '&#1052;&#1072;&#1088;&#1080;&#1085;&#1072; &#1054;&#1088;&#1083;&#1086;&#1074;&#1072;'; echo "<p>author (85 bytes):$the_string," . strlen($the_string) . ',' . strlen( utf8_decode( $the_string ) ) . ',' . strlen( utf8_decode( utf8_encode($the_string) ) ) . ',' . "</p>"; // all the number echoed are 85, I expected at least one to be 13 $max_length = 20; $is_short = preg_match( '/^.{1,$max_length}$/u', uft8_encode( $the_string ) ) ); // expect the above to return 1 $max_length = 10; $is_short = preg_match( '/^.{1,$max_length}$/u', uft8_encode( $the_string ) ) ); // expect the above to return 0 ?> More generally, given a string $the_string: 2) how to determine what encoding is being used? 3) how to determine the number of visible characters? 4) if it has more than N visible characters, how to truncate it after N visible characters? Thanks!