In addition to Sezer Yalcin's tip.
This function splits a multibyte string into an array of characters. Comparable to str_split().
<?php
function mb_str_split( $string ) {
# Split at all position not after the start: ^
# and not before the end: $
return preg_split('/(?<!^)(?!$)/u', $string );
}
$string = '火车票';
$charlist = mb_str_split( $string );
print_r( $charlist );
?>
# Prints:
Array
(
[0] => 火
[1] => 车
[2] => 票
)