update : 2015.11.03
PHP 5.3 introduced some new functions:
- Clears IMAP cache.
- Encode a UTF-8 string to modified UTF-7.
- Decode a modified UTF-7 string to UTF-8.
- Perform a regular expression search and replace, returning only results
which matched the pattern.
The following functions are now natively implemented, making them available
on all operating systems which can run PHP: