PHP UTF-8 Questions - If I create a string in PHP ... is it in UTF-8?

Question

In PHP, if I create a line like this:

 $ str = "bla bla here is my string";

Will I be able to use mbstring functions to work with this line as UTF8?

 // Will this work?
 $ str = mb_strlen ($ str); 

Also, if I have another row that I know is UTF-8 (let's say this is a POSTED value of a form or a UTF-8 row from a database), can I then combine the two and not have any problems?

 // What about this, will this work? 
 $ str = $ str.  $ utf8_string_from_database;

Answer 1

First question: it depends on what exactly goes on the line.

In PHP (up to PHP5, anyway) strings are just sequences of bytes. An implied or explicit character set is not associated with them; what the programmer should keep track of. So, if you put only valid UTF-8 bytes between quotation marks (quite easily if the file itself is encoded as UTF-8), then the line will be UTF-8, and you can safely use mb_strlen () on it.

Also, if you use the mbstring functions, you need to explicitly specify which character your string specifies, either mbstring.internal_encoding or as the last argument to any mbstring function.

The second question: yes, with reservations.

Two strings that are independently valid UTF-8 can be safely combined bytes (for example, with the PHP operator . ) And are still valid for UTF-8. However, you can never be sure without doing any work yourself that the POSTed line is valid UTF-8. Database rows are a little simpler if you carefully set the connection character set, since most DBMSs will do any conversion for you.

Answer 2

If your source code is in UTF-8, then the line is in UTF-8, if not, it is not. Since the line of your example is used only in English, it is valid UTF-8.

PHP itself does not know about encodings. If you pass stuff to the mb * function, it treats it as a UTF-8 string.

Concatenation should work fine, no matter what, if I understand UTF-8 correctly :-) Just make sure that both lines are UTF-8, otherwise you will get a strange string as a result.

Answer 3

Make sure the default_charset directive is set to UTF-8 before any of these actions occur.

Either modify php.ini directly, or execute it at runtime with

 <?php ini_set( 'default_charset', 'UTF-8' );