The biggest difference is in handling of entities. Entities are now unescaped before passing to expressions, i.e. ${php:strlen('"')} “sees” just the quote character and returns 1. In previous versions entities were passed as-is to the expressions (and that example would return 6).

Newly added unescaping of entities can expose encoding bugs. Make sure your pages declare document encoding: For XHTML it's best to send Content-Type:application/xhtml+xml;charset=UTF-8 or Content-Type:text/html;charset=UTF-8 HTTP headers.

• Don't use text/xml MIME type, use application/xml instead.

In HTML add appropriate <meta> tag or send Content-Type:text/html;charset=UTF-8 HTTP header.

• If you're not using UTF-8 encoding, you must set encoding you use via $phptal->setEncoding('ISO-8859-…') (or just switch to UTF-8 already! :)

• Only some 8-bit-based encodings are supported. If your encoding is not supported, you may get away with setting ISO-8859-1 instead.

• All constants except PHPTAL_VERSION have been removed. Remove any PHPTAL-specific define()s and use class methods (available in earlier versions too) for configuration (e.g. $phptal->setPhpCodeDestination('/tmp/phptal/') for custom temp directory.)

• PHPTAL_DIR is gone. PHPTAL now temporarily modifies include_path (this may change in the future).

• Don't include any PHPTAL's files before including PHPTAL.php.

• XML namespace of phptal:* attributes has changed from http://xml.zope.org/namespaces/phptal to http://phptal.motion-twin.com/ns/phptal.

• Comments are required to be well-formed (-- is not allowed in comments.) Comments starting with <!--! are stripped from output.

• tal:repeat doesn't “leak” variables to outer scope
• Internal DOM classes have been refactored. Your custom TAL attributes could break – if they did, please complain on the mailinglist!