PHP 5.6 new features

New Constant options

<?php
/* 
 * A few additon of how you can work using constants
 */
const ONE = 1;         // Regular constant
const TWO = ONE * 2;    // New feature
const ARR = ['a', 'b']; // Possible to define Array Constants

class C {
 // As properties
 const THREE = TWO + 1;
 const ONE_THIRD = ONE / self::THREE;
 onst SENTENCE = 'The value of THREE is '.self::THREE;

 // As default function arguments
 public function f($a = ONE + self::THREE) {
   return $a;
 }
}

echo (new C)->f(); // Outputs: 4
echo C::SENTENCE;  // Outputs: The value of THREE is 3

More info on Constants

Variadic functions via "..." operator

<?php
/*
 * This a new way to create functions with a variable number of arguments.
 */
function sum(...$numbers) {
  $acc = 0;
  foreach ($numbers as $n) {
    $acc += $n;
  }
  return $acc;
}
echo sum(1, 2, 3, 4); // Outputs: 10

// ---------------------------------------------------------------

function f($req, $opt = null, ...$params) {
  // $params is an array containing the remaining arguments.
  echo count($params);
}

f(1);             // outputs: 0
f(1, 2);          // outputs: 0
f(1, 2, 3);       // outputs: 1
f(1, 2, 3, 4);    // outputs: 2
f(1, 2, 3, 4, 5); // outputs: 3

More info on Variadic functions

Argument unpacking via "..." operator

<?php
/*
 * Arrays and Traversable objects can be unpacked into argument
 * lists when calling functions by using the ... operator. 
 * This is called splat operator in other languages.
 */
function add($a, $b, $c) {
  return $a + $b + $c;
}

$operators = [2, 3];
echo add(1, ...$operators);

Exponentiation via **

<?php
/*
 * A right associative ** operator has been added to support exponentiation,
 * along with a **= shorthand assignment operator. 
 */
echo 2 ** 3; // outputs 8

$a = 2;
$a **= 3; // $a value is 8

'use function' and 'use const'

<?php
/*
 * The use operator has been extended to support importing functions
 * and constants in addition to classes. 
 */
namespace Name\Space {
  const FOO = 42;
  function f() { return 0 }
}

namespace {
  use const Name\Space\FOO;
  use function Name\Space\f;

  // .. Use FOO and f();
}

For a full list of changes go here.