Description:
------------
I think there are a couple of omissions that could be added to the notes here:
 http://www.php.net/language.types.string

1. Clarify that, unlike C-strings, PHP-strings are properly binary safe, i.e. not internally null-terminated, and can include embedded \0.   One might otherwise wrongly expect that, for example strlen("hello\0world") would be 5.

2. The reference to PHP's strings not being natively Unicode is a bit confusing: a string is just a sequence of bytes, and doesn't, conceptually, even have a character set! UTF-8 is already transparently ASCII compatible as a byte-stream. It's just certain functions (strlen, strtolower etc) that can't cope. 
[May I suggest a reference to the UTF-8 FAQ: http://www.cl.cam.ac.uk/~mgk25/unicode.html )