Number of characters in a string

[Tleilaxu]

    $string = 'six@lgfhfget@;][';
    $string_count = strlen(ereg_replace('[^[:alpha:]]+', '', $string));
    echo $string_count; 

Thank you, but is not working.

It returns 0 length for UTF-8 entries like this: 後味 (it should return 2)