ref

• 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.
• 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

ref

• Generators added
• finally keyword added
• foreach now supports list()
• empty() supports arbitrary expressions
• Class name resolution via ::class

ref

• Constant expressions
• Variadic functions via …
• Argument unpacking via …
• Exponentiation via **
• use function and use const

ref

• Scalar type declarations
• Return type declarations
• Null coalescing operator
• Spaceship operator
• Constant arrays using define()
• Anonymous classes
• Closure::call()
• Expectations
• Group use declarations

http://docs.php.net/manual/en/migration71.new-features.php