PHP 5.1 Release Candidate 1 is now available! If all goes well, this RC will be followed by a release within a couple of weeks.

Some of the key improvements of PHP 5.1 include:

• PDO (PHP Data Objects) - A new native database abstraction layer providing performance, ease-of-use, and flexibility.
• Significantly improved language performance mainly due to the new Zend Engine II execution architecture.
• The PCRE extension has been updated to PCRE 6.2.
• Many more improvements including lots of new functionality & many bug fixes, especially in regards to SOAP, streams and SPL.
• See the bundled NEWS file for a more complete list of changes.

Everyone is encouraged to download and test this beta, although it is not yet recommended for mission-critical production use.