On the main PHP site today, there's the announcement of PHP 5.1.1 being released for public consumption.

The PHP Development Team would like to announce the immediate release of PHP 5.1.1.

This is a regression correction release aimed at addressing several issues introduced by PHP 5.1.0, the core changes as follows:

• Native date class is withdrawn to prevent namespace conflict with PEAR's date package.
• Fixed fatal parse error when the last line of the script is a PHP comment.
• eval() hangs when the code being evaluated ends with a comment.
• Usage of \{$var} in PHP 5.1.0 resulted in the output of {$var} instead of the $var variable's value enclosed in {}.
• Fixed inconsistency in the format of PHP_AUTH_DIGEST between Apache 1 and 2 sapis.
• Improved safe_mode/open_basedir checks inside the cURL extension.

So, if you grabbed the PHP 5.1.0 release the other day, go ahead and pull this one down - there are a few smaller bug fixes that were done, but a few majors that could cause problems down the line..