New features

PHP 5.4.0 offers a wide range of new
features:

• Support for traits has been
  added.
• Short array syntax has
  been added, e.g. $a = [1, 2, 3, 4]; or $a = [‘one’
  => 1, ‘two’ => 2, ‘three’ => 3, ‘four’ =>
  4];.
• Function array
  dereferencing has been added, e.g. foo()[0].
• Closures now support
  $this.
• <?= is now
  always available, regardless of the short_open_tag
  php.ini option.
• Class member access on
  instantiation has been added, e.g. (new
  Foo)->bar().
• Class::{expr}()
  syntax is now supported.
• Binary number format has
  been added, e.g. 0b001001101.
• Improved parse error
  messages and improved incompatible arguments warnings.
• The session extension
  can now track the upload progress of files.
• Built-in development
  web
  server in CLI mode.
• The GD extension now
  supports reading and writing of WebP images via imagecreatefromwebp() and imagewebp(), respectively.