PHP 5.3.0 offers a wide range of new features:
Support for namespaces has been added.
Support for Late Static Bindings has been added.
Support for jump labels (limited goto) has been added.
Support for native Closures (Lambda/Anonymous functions) has been added.
There are two new magic methods, __callStatic() and __invoke().
Nowdoc syntax is now supported, similar to Heredoc syntax, but with single quotes.
It is now possible to use Heredocs to initialize static variables and class properties/constants.
Heredocs may now be declared using double quotes, complementing the Nowdoc syntax.
Constants can now be declared outside a class using the const keyword.
The ternary operator now has a shorthand form: ?:.
The HTTP stream wrapper now considers all status codes from 200 to 399 to be successful.
Dynamic access to static methods is now possible.
Exceptions can now be nested.
A garbage collector for circular references has been added, and is enabled by default.
The mail() function now supports logging of sent email. (Note: This only applies to email sent through this function.)