1)Constant Array
===============
Now the constant data types in php can be defined as numerically indexed array and associative array.

So below line of code can be coded like as new constant array.

old
------
<?php
define('COLOR_RED', '#f44141');
define('COLOR_BLUE', '#4286f4');
define('COLOR_GREEN', '#1ae01e');
define('COLOR_PURPLE', '#f309f7');
define('COLOR_ORANGE', '#ef7700');

New Way
------
<?php
// As an associative array
define('COLORS', [
    'red' => '#f44141',
    'blue' => '#4286f4',
    'green' => '#1ae01e',
    'purple' => '#f309f7',
    'orange' => '#ef7700',
]);

echo(COLORS['red']); // #f44141


// As indexed array
define('COLORS', [
    'red',
    'blue',
    'green',
    'purple',
    'orange',
]);

echo(COLORS[0]); // 'red'


2) Group use declaration
=========================
Previously we need to use single statement for importing class, function or variable like below code,

<?php
use VendorName/LibraryName/ClasName1;
use VendorName/LibraryName/ClasName2;
use VendorName/LibraryName/ClasName3;

Now we can use latest grouping method as seen below
------------------------------------
<?php
use VendorName/LibraryName/{ClasName1, ClassName2. ClassName3};


3)NULL Check operator
====================
PHP will throw an error about an undefined variable, index, if the variable is not defined or empty.
so we need to check below code for safe code running.

Old method
----------
<?php
if(!isset($_GET['key'])) {
    $key = 'default-value';
} else {
    $key = $_GET['key'];
}

We can use ternary operator to check this null case. but even we need to add isset function in ternarry

PHP now introduced the new " Null Coalescing Operator ( ?? ) " to check the null case.

New method
----------
<?php
$key = $_GET['key'] ?? 'default_value';

You can also use below code for chained checking


<?php
if (isset($_GET['key']) {
    $key = $_GET['key'];
} else if(isset($_POST['key'])) {
    $key = $_POST['key'];
} else {
    $key = 'default value';
}

// Versus

$key = $_GET['key'] ?? $_POST['key'] ?? 'default value';


4)Return Type Declarations and Coercive for PHP function:
================================================

This will force the function to accept the argument type and return type of the function.
eg:

<?php
function reverseString(String $str) : String {
    return strrev($str);
}
print(reverseString(1234));


The above function will accept only string value and returns the string value.
Now Here the number 1234 is passed it will coerced into string '1234' and returns string.

As analogus to strict used in the javascript, in PHP we can declare the strict method for function.
Eg below.

<?php
declare(strict_types=1);
function reverseString(String $str) : String {
    return strrev($str);
}
print(reverseString(1234));

This will check the argument is string and if not report a fatal error and stop execution.