== is used for check equality without considering variable data-type

=== is used for check equality for both the variable value and data-type

Example

$a = 5

1. if ($a == 5) - will evaluate to true

2. if ($a == '5') - will evaluate to true, because while comparing this both value PHP internally convert that string value into integer and then compare both values

3. if ($a === 5) - will evaluate to true

4. if ($a === '5') - will evaluate to false, because value is 5, but this value 5 is not an integer.

Nullable return type declaration

PHP 7 adds support for return type declarations. Similarly to argument type declarations, return type declarations specify the type of value that will be returned from a function. The same types are available for return type declarations as are available for argument type declarations.

Strict typing also has an effect on return type declarations. In the default weak mode, returned values will be coerced to the correct type if they are not already of that type. In strong mode, the returned value must be of the correct type, otherwise, a TypeError will be thrown.

As of PHP 7.1.0, return values can be marked as nullable by prefixing the type name with a question mark (?). This signifies that the function returns either the specified type or NULL.

<?php
function get_item(): ?string {
    if (isset($_GET['item'])) {
        return $_GET['item'];
    } else {
        return null;
    }
}
?>

Source

?-> NullSafe Operator

Added in PHP 8.0

It's the NullSafe Operator, it returns null in case you try to invoke functions or get values from null. Nullsafe operator can be chained and can be used both on the methods and properties.

$objDrive = null;
$drive = $objDrive?->func?->getDriver()?->value; //return null
$drive = $objDrive->func->getDriver()->value; // Error: Trying to get property 'func' of non-object

Nullsafe operator doesn't work with array keys:

$drive['admin']?->getDriver()?->value //Warning: Trying to access array offset on value of type null

$drive = [];
$drive['admin']?->getAddress()?->value //Warning: Undefined array key "admin"

Three DOTS as Splat Operator (...) (since PHP 5.6)

PHP has an operator "..." (Three dots) which is referred as Splat Operator. It is used to pass arbitrary number of parameters in a function and this type of function is called Variadic Functions. Let’s take examples to use of "..." (Three dots).

Example 1:

<?php
function calculateNumbers(...$params){
    $total = 0;
    foreach($params as $v){
        $total = $total + $v;
    }
    return $total;
}
 
echo calculateNumbers(10, 20, 30, 40, 50);
 
//Output 150
?>

Each arguments of calculateNumbers() function pass through $params as an array when use "… ".

There are many different ways to use "… " operator. Below some examples:

Example 2:

<?php
function calculateNumbers($no1, $no2, $no3, $no4, $no5){
    $total = $no1 + $no2 + $no3 + $no4 + $no5;
    return $total;
}
 
$numbers = array(10, 20, 30, 40, 50);
echo calculateNumbers(...$numbers);
 
//Output 150
?>

Example 3:

<?php
function calculateNumbers(...$params){
    $total = 0;
    foreach($params as $v){
        $total = $total + $v;
    }
    return $total;
}
$no1 = 70;
$numbers = array(10, 20, 30, 40, 50);
echo calculateNumbers($no1, ...$numbers);
 
//Output 220
?>

Example 4:

<?php
function calculateNumbers(...$params){
    $total = 0;
    foreach($params as $v){
        $total = $total + $v;
    }
    return $total;
}
 
$numbers1 = array(10, 20, 30, 40, 50);
$numbers2 = array(100, 200, 300, 400, 500);
echo calculateNumbers(...$numbers1, ...$numbers2);
 
//Output 1650
 
?>

It should be noted that Variadic Parameters cannot be targeted by named arguments.

Example 5:

<?php
function sumIntegers(int ...$params): int {
    $sum = 0;
    foreach($params as $value){
        $sum += $value;
    }
    return $sum;
}


echo sumIntegers(params: [1, 2, 3, 4]);     
// $params will be equal to ['params' => [1, 2, 3, 4]] in sumIntegers
// throws TypeError sumIntegers(): Argument #1 must be of type int, array given 

echo sumIntegers(arbitrary_name: 1, another_name: 2);
// $params will be equal to ['arbitrary_name' => 1, 'another_name' => 2] in sumIntegers
// Outputs: 3 
?>

Using an unpacked associative array as the parameter for a function call has the same effect as calling the function using each key-value pair as a named argument.

Example 6:

<?php
function fullName(string $first_name, ?string $middle_name = null, ?string $last_name = null): string {
    return trim("$first_name|$middle_name|$last_name");
}

$params = ['first_name' => 'John', 'last_name' => 'Doe'];
echo fullName(...$params);
// same as fullName(first_name: 'John', last_name: 'Doe')

// outputs 'John||Doe'
?>

This can be used to pass named arguments to something like a nested function call or a class.

Example 7:

<?php
function throw_exception(string $exception, ...$parameters) {
    throw new $exception(...$parameters);
}

throw_exception(exception: 'Exception', code: 123);
// executes throw new Exception(...['code' => 123])
// which is the same as throw new Exception(code: 123);
?>

NullSafe Operator "?->" since php8

In PHP8 it's been accepted this new operator, you can find the documentation here. ?-> it's the NullSafe Operator, it returns null in case you try to invoke functions or get values from null...

Examples:

<?php
$obj = null;
$obj = $obj?->attr; //return null
$obj = ?->funct(); // return null
$obj = $objDrive->attr; // Error: Trying to get property 'attr' of non-object
?>

#[] attributes since PHP 8

You can write #[attribute_name] since PHP 8. This is an attribute in PHP (also Rust and C#). Other languages may use names like annotations (Java) or decorators (Python, Javascript) for a similar feature. Prior to PHP 8, #[whatever] would have been a comment until the end of the line (because # starts a comment in PHP). So if an attribute is the last thing on a line, it will be ignored in versions before PHP 8. If not the last thing on a line, it would comment out whatever was after it prior to PHP 8 (since then the ] terminates it).

• RFC
• Syntax RFC (the syntax was changed from the original RFC)
• Documentation

In php 8

Instead of writing the classic !== null you can use the ? operator to write just 1 line of code, the code becomes pretty clear:

Before:

$firsName =  null;
if ($session !== null) {
    $user = $session->user;
    if ($user !== null) {
        $name = $user->getName();
        if ($name !== null) {
            $firstName = $name->firstName;
        }
    }
}

After:

$firsName = $session?->user?->getName()?->firstName;

Use match instead of switch. The match expression uses strict comparison (===) instead. The comparison is strict regardless of strict_types.

Before:

switch ('A') {
    case 'A':
        echo "found A";
        break;
    case 'B':
        echo "found B";
        break;
}
// Result: "found A"

After:

echo match ('A') {
  'A' => "found A",
  'B' => "found B",
};
// Result: "found A"

Double-dot syntax

When used between two characters in qualifying native PHP string functions, .. acts to express an inclusive range of characters. a-e is equivalent to abcde.

echo trim('adobe', 'a..e');

Prints:

o

Native PHP functions that allow double-dot range syntax