What's new in PHP 8.4

January 8, 2024 · PHP

PHP 8.3 has already been released a few months back and it’s time to look at what’s coming in PHP 8.4.

It’s not a lot of features so far but there are some interesting ones. I’ll be updating this article as more features are added to the PHP 8.4 release. So, make sure you bookmark this article.

• New modes for the round() function
• A new way to disable JIT
• A new JIT implementation
• A new option to parse huge XMLs
• Multibyte equivalents for the trim() function
• A new class for parsing and serializing HTML5
• Multibyte for ucfirst and lcfirst functions
• Grapheme cluster for str_split function
• Dedicated functions for HTTP response headers
• Calling methods on newly instantiated class without parentheses
• New array functions
• Property hooks
• A new #[\Deprecated] attribute
• Implicitly nullable parameter types will be deprecated
• Separate visibilities for read and write operations on properties
• exit() is now a standard function
• A new Enum for rounding modes
• Raising zero to the power of negative number will give deprecation warning
• A new function to allow parsing of multipart/form-data content type for non-POST requests
• A dedicated class for stream processing
• Session propagation will no longer be done using GET/POST requests
• A new function to efficiently calculate both the quotient and remainder in a single operation
• Improvements to the XMLReader and XMLWriter classes
• Some extensions are going away from PHP core
• Introduction of Lazy Objects
  • Creating Lazy Objects
  • Handling the State of Lazy Objects
  • Lifecycle of Lazy Objects
  • A real-world usage of Lazy Objects

New modes for the round() function

The round() function is used to round a number to its nearest integer. It’s a very common function used in PHP.

Up until now, the round() function had only four rounding modes: PHP_ROUND_HALF_UP, PHP_ROUND_HALF_DOWN, PHP_ROUND_HALF_EVEN, and PHP_ROUND_HALF_ODD.

In PHP 8.4, four more rounding modes will be added to the round() function.

• PHP_ROUND_CEILING - This will round the number to the nearest integer bigger than the given number. So, round(1.3, 0, PHP_ROUND_CEILING) will return 2 since 2 is the nearest integer bigger than 1.3.

• PHP_ROUND_FLOOR - This will round the number to the nearest integer smaller than the given number. So, round(1.3, 0, PHP_ROUND_FLOOR) will return 1 since 1 is the nearest integer smaller than 1.3.

• PHP_ROUND_AWAY_FROM_ZERO - This will round the number away from zero. So, round(1.3, 0, PHP_ROUND_AWAY_FROM_ZERO) will return 2 since 2 is away from zero and is the nearest integer.

• PHP_ROUND_TOWARD_ZERO - This will round the number towards zero. So, round(1.3, 0, PHP_ROUND_TOWARD_ZERO) will return 1 since 1 is towards zero and is the nearest integer.

To simplify this further, PHP 8.4 also introduces a dedicated Enum to explicitly name the rounding modes that accurately describe the rounding behavior without the need for documentation.

Read RFC

A new way to disable JIT

PHP 8.0 introduced JIT (Just In Time) compilation which is a technique that converts PHP code into machine code at runtime. This improves the performance of PHP code.

So, you can change a lot of different configurations related to JIT in the php.ini file but the current way of disabling JIT is a little bit confusing.

You can do it by setting the opcache.jit_buffer_size to 0 in the php.ini file. But this is not very intuitive.

opcache.jit=tracing
opcache.jit_buffer_size=0

To make it more intuitive, PHP 8.4 will introduce a new configuration directive called disable which will disable JIT.

opcache.jit=disable
opcache.jit_buffer_size=64m

Here, the default value for opcache.jit_buffer_size is also updated to 64m from 0.

Read RFC

A new JIT implementation

This change is not a user-facing change but it’s worth mentioning here.

PHP 8.4 will attempt to implement a new JIT implementation based on the IR (Intermediate Representation) framework. This new implementation is said to be “smarter” than the current one.

This implementation only uses a single back-end that constructs IR to generate x86 and AArch64 code as opposed to the current implementation which uses two back-ends.

Read RFC

A new option to parse huge XMLs

PHP 8.4 will introduce a new option called XML_OPTION_PARSE_HUGE that can be passed along to xml_parser_set_option while parsing XMLs.

Here’s how this looks like.

function startElement($parser, $name, $attrs)
{
    // Do something interesting
}

function endElement($parser, $name) 
{
    // Do something interesting
}

$parser = xml_parser_create();
xml_parser_set_option($parser, XML_OPTION_PARSE_HUGE, true); 
// Changing this to false, or not executing this line, 
// will cause the parsing to error out on large inputs

xml_set_element_handler($parser, "startElement", "endElement");
// Add more handlers

$success = xml_parse($parser, $my_long_xml_input_already_in_memory);

This option will allow you to parse huge XMLs without running into memory issues or running into parsing errors.

Read RFC

Multibyte equivalents for the trim() function

PHP has always been lacking multibyte equivalents for the trim() function. But in PHP 8.4, this will be fixed.

The following three functions will be added to PHP 8.4.

• mb_trim() - Same as trim() but for multibyte strings. It will remove all whitespace characters from the beginning and end of a string.

Here’s the entire signature of the function.

function mb_trim(string $string, string $characters = " \f\n\r\t\v\x00\u{00A0}\u{1680}\u{2000}\u{2001}\u{2002}\u{2003}\u{2004}\u{2005}\u{2006}\u{2007}\u{2008}\u{2009}\u{200A}\u{2028}\u{2029}\u{202F}\u{205F}\u{3000}\u{0085}\u{180E}"): string

• mb_ltrim() - Same as ltrim() but for multibyte strings. It will remove all whitespace characters from the beginning of a string.

Here’s the entire signature of the function.

function mb_ltrim(string $string, string $characters = " \f\n\r\t\v\x00\u{00A0}\u{1680}\u{2000}\u{2001}\u{2002}\u{2003}\u{2004}\u{2005}\u{2006}\u{2007}\u{2008}\u{2009}\u{200A}\u{2028}\u{2029}\u{202F}\u{205F}\u{3000}\u{0085}\u{180E}", ?string $encoding = null): string

• mb_rtrim() - Same as rtrim() but for multibyte strings. It will remove all whitespace characters from the end of a string.

Here’s the entire signature of the function.

function mb_rtrim(string $string, string $characters = " \f\n\r\t\v\x00\u{00A0}\u{1680}\u{2000}\u{2001}\u{2002}\u{2003}\u{2004}\u{2005}\u{2006}\u{2007}\u{2008}\u{2009}\u{200A}\u{2028}\u{2029}\u{202F}\u{205F}\u{3000}\u{0085}\u{180E}", ?string $encoding = null): string

Read RFC

A new class for parsing and serializing HTML5

Up until now, PHP’s DOM extension is kind of stuck with the HTML4 specification. That is the DOMDocument class can only parse and serialize HTML4 documents.

But since HTML5 is the new standard, PHP 8.4 will introduce a new class called DOM\HTMLDocument that can parse and serialize HTML5 documents.

Here’s how this looks like.

namespace DOM {
	// The base abstract document class
	abstract class Document extends DOM\Node implements DOM\ParentNode {
		/* all properties and methods that are common and sensible for both XML & HTML documents */
	}
 
	final class XMLDocument extends Document {
		/* insert specific XML methods and properties (e.g. xmlVersion, validate(), ...) here */
 
		private function __construct() {}
 
		public static function createEmpty(string $version = "1.0", string $encoding = "UTF-8"): XMLDocument;
		public static function createFromFile(string $path, int $options = 0, ?string $override_encoding = null): XMLDocument;
		public static function createFromString(string $source, int $options = 0, ?string $override_encoding = null): XMLDocument;
	}
 
	final class HTMLDocument extends Document {
		/* insert specific Html methods and properties here */
 
		private function __construct() {}
 
		public static function createEmpty(string $encoding = "UTF-8"): HTMLDocument;
		public static function createFromFile(string $path, int $options = 0, ?string $override_encoding = null): HTMLDocument;
		public static function createFromString(string $source, int $options = 0, ?string $override_encoding = null): HTMLDocument;
	}
}
 
class DOMDocument extends DOM\Document {
	/* Keep methods, properties, and constructor the same as they are now */
}

Read RFC

Multibyte for ucfirst and lcfirst functions

PHP has always been lacking multibyte equivalents for the ucfirst() and lcfirst() functions. But in PHP 8.4, this will be fixed.

The following two functions will be added to PHP 8.4.

• mb_ucfirst() - Same as ucfirst() but for multibyte strings.

function mb_ucfirst(string $string, ?string $encoding = null): string

• mb_lcfirst() - Same as lcfirst() but for multibyte strings.

function mb_lcfirst(string $string, ?string $encoding = null): string

Here are some examples of how these functions will work.

mb_ucfirst(“აბგ”); // prints “აბგ” (U+10D0 U+10D1 U+10D2)
mb_ucfirst(“lj”) // prints “Lj” (U+01C9 -> U+01C8)

Grapheme cluster for str_split function

A grapheme cluster is a collection of symbols that together represent an individual character that the user will see within a string on the screen.

PHP was lacking a str_split function that would return an array of grapheme clusters. PHP 8.4 will introduce a new function called grapheme_str_split() that will return an array of grapheme clusters.

Here’s the signature of the function.

function grapheme_str_split(string $string, int $length = 1): array|false {}

$string only supports UTF-8. $length is the length of the grapheme cluster per element of the array.

Here is an example of how this function will work.

var_dump(grapheme_str_split("🙇‍♂️"));

/*
  [0]=>
  string(13) "🙇‍♂️"
}
*/

One more example.

var_dump(grapheme_str_split("ä-pqr-b̈-xyz-c̈"));

/*
array(13) {
  [0]=>
  string(2) "ä"
  [1]=>
  string(1) "-"
  [2]=>
  string(1) "p"
  [3]=>
  string(1) "q"
  [4]=>
  string(1) "r"
  [5]=>
  string(1) "-"
  [6]=>
  string(3) "b̈"
  [7]=>
  string(1) "-"
  [8]=>
  string(1) "x"
  [9]=>
  string(1) "y"
  [10]=>
  string(1) "z"
  [11]=>
  string(1) "-"
  [12]=>
  string(3) "c̈"
}

Dedicated functions for HTTP response headers

Instead of automatically creating a $http_response_header variable in the local scope while an HTTP request is performed through PHP’s stream layer, i.e. when using the HTTP wrapper (one such usage is using file_get_contents() to retrieve the content of a URL), two new functions have been added to PHP 8.4.

• http_get_last_response_header() - Returns the last response headers as an array.
• http_clear_last_response_headers() - Clears the last response headers.

Here’s what the response would look like.

$response = http_get_last_response_header();

var_dump($response);

/*
array(9) {
  [0]=>
  string(15) "HTTP/1.1 200 OK"
  [1]=>
  string(35) "Date: Sat, 12 Apr 2008 17:30:38 GMT"
  [2]=>
  string(29) "Server: Apache/2.2.3 (CentOS)"
  [3]=>
  string(44) "Last-Modified: Tue, 15 Nov 2005 13:24:10 GMT"
  [4]=>
  string(27) "ETag: "280100-1b6-80bfd280""
  [5]=>
  string(20) "Accept-Ranges: bytes"
  [6]=>
  string(19) "Content-Length: 438"
  [7]=>
  string(17) "Connection: close"
  [8]=>
  string(38) "Content-Type: text/html; charset=UTF-8"
}
*/

Calling methods on newly instantiated class without parentheses

Up unitl now, when you want to call a method on a newly instantiated class without parentheses, you had to do it like this.

$obj = (new MyClass())->myMethod();

While this will still work, PHP 8.4 will let you call a method on a newly instantiated class without parentheses.

So, previous example will look like this.

$obj = new MyClass()->myMethod();

It just looks a bit cleaner in my opinion.

Here are all the places where this will work.

new MyClass()::CONSTANT;  
new MyClass()::$staticProperty; 
new MyClass()::staticMethod();  
new MyClass()->property;      
new MyClass()->method();      
new MyClass()();              
new MyClass(['value'])[0];

Read RFC

New array functions

PHP 8.4 will introduce a few new array functions which are helper functions for common patterns of checking an array for the existence of elements matching a specific condition.

The new methods are:

• array_find - Returns the value of the first element for which the $callback returns true. If no matching element is found the function returns NULL.
• array_find_key - Returns the key of the first element for which the $callback returns true.
• array_any - Returns true if any of the elements in the array pass the $callback test. Otherwise, it returns false.
• array_all - Returns true if all of the elements in the array pass the $callback test. Otherwise, it returns false.

I have covered these functions in a dedicated article: A few new array functions are making their way into PHP 8.4.

Property hooks

PHP 8.4 will introduce property hooks that allows you to define custom logic for property access and mutation. This can be useful for a variety of use cases, such as mutation, logging, validation, or caching.

Essentially, property hooks allow you to define additional behavior on class properties mainly using two hooks: get and set. And this will be individual for certain properties.

Here’s how a set hook looks like.

class User
{
    public string $email {
        set (string $value) {
            // validate the email address
            if (!filter_var($value, FILTER_VALIDATE_EMAIL)) {
                throw new InvalidArgumentException(
                    'Invalid email address'
                );
            }
            
            // Set the value
            $this->email = $value;
        }
    }
}

And here’s how it works when setting the value of the $email property.

$user = new User();
$user->email = 'example.com'; // This will throw an exception

$user = new User();
$user->email = '[email protected]';
echo $user->email; // [email protected]

You can learn more about property hooks in the dedicated article.

A new #[\Deprecated] attribute

PHP 8.4 will introduce a new attribute called #[\Deprecated] that can be used to mark functions, classes, and constants as deprecated.

Meaning, once the function, class, or constant is marked as deprecated, it will give a deprecation warning when the function, class, or constant is used.

Here’s how this looks like.

class User
{
    #[\Deprecated]
    public function getSession(): string
    {
        return 'session';
    }

    #[\Deprecated('Use getUser() instead')]
    public function getUsername(): string
    {
        return $this->username;
    }
}

$user = new User();
$user->getUsername(); 
// Deprecated: Use getUser() instead

$user->getSession();
// Deprecated: Function getSession() is deprecated

As you can tell, you can use the #[\Deprecated] with your own message to better explain why the function, class, or constant is deprecated.

You can also check if a function, class, or constant is deprecated programmatically by using reflection.

#[\Deprecated]
function test() {
}
 
$r = new ReflectionFunction('test');
 
var_dump($r->isDeprecated()); // bool(true)

Read RFC

Implicitly nullable parameter types will be deprecated

PHP 8.4 will deprecate implicitly nullable parameter types. This means that when you define a parameter in a function or method and assign null as a default value, you will get a deprecation warning.

Here’s how this looks like.

function test(T $value = null) {
    // Do something
}

// Deprecated: Implicitly marking parameter $value 
// as nullable is deprecated, the explicit nullable 
// type must be used instead

To get rid of this warning, you will have to use the explicit nullable type like so.

function test(?T $value) {
    // Do something
}

Read RFC

Separate visibilities for read and write operations on properties

PHP 8.4 will bring in an ability to define separate visibilities for read and write operations on properties. This means that you can define a property as public and private for read and write operations respectively. It’s called “asymmetric visibility”.

This is how it works.

class Foo
{
    public private(set) string $bar = 'baz';
}
 
$foo = new Foo();
var_dump($foo->bar); // prints "baz"
$foo->bar = 'beep'; // Visibility error

Essentially, you can now declare the “set” operation visibility of an object property to limit the visibility.

In this example, the set operation is limited to private and the get operation is limited to public. So, you can access the property from the public scope without any issues but you can’t set the value of the property from the public scope.

This works same for protected as well.

Apart from this, if a set visibility is specified on a property then a public get visibility may be omitted. So, both the following statements are equivalent.

public private(set) string $bar = 'baz';
private(set) string $bar = 'baz';

Here’s a more practical example of how this can be used.

class User
{
    public function __construct(
        // The user's email can only be set internally by the class,
        // but it can be read publicly
        public private(set) string $email
    ){}

    // Method to change the email, ensuring only valid updates are done
    public function updateEmail(string $newEmail)
    {
        if (filter_var($newEmail, FILTER_VALIDATE_EMAIL)) {
            $this->email = $newEmail;
        } else {
            throw new Exception('Invalid email format.');
        }
    }
}

$user = new User('[email protected]');
var_dump($user->email); 
// prints "[email protected]"

// This would result in an error, 
// since the property is read-only from outside
$user->email = '[email protected]'; // Visibility error

// Proper way to update email via the class's method
$user->updateEmail('[email protected]');
var_dump($user->email); 
// prints "[email protected]"

Read RFC

exit() is now a standard function

The current exit() construct does not behave like a standard function, leading to confusion and inconsistency, especially in type handling and error messaging.

So, PHP 8.4 will introduce exit() as a proper function with a defined signature, allowing for named arguments, compatibility with strict_types, and adherence to standard type juggling semantics. The behavior of exit() will be like a typical function, including the ability to be passed as a callable and respecting type juggling for arguments.

function exit(string|int $status = 0): never {}

The new function will maintain the same parsing and will not be removable via the disable_functions INI directive.

As per the RFC, the impact of this change to the backward compatibility will be fairly low with the future scope being deprecating the use of exit without parentheses, executing finally blocks when exit is called, and the ability to disable exit()/die() funuctions via disable_functions INI directive.

Read RFC

A new Enum for rounding modes

PHP 8.4 will rename rounding modes of the round() function for clarity and consistency, and to implement them as an Enum in PHP 8.4, enhancing type safety and usability.

PHP currently have four rounding modes (PHP_ROUND_HALF_UP, PHP_ROUND_HALF_DOWN, PHP_ROUND_HALF_EVEN, and PHP_ROUND_HALF_ODD), which suffer from two main issues:

• The use of integers for rounding modes, leading to potential misuse
• The counterintuitive behavior of “up” and “down” modes for negative values.

This RFC suggests the introduction of a RoundingMode enum in the core to replace the existing integer constants, providing explicit names that accurately describe the rounding behavior without the need for documentation.

enum RoundingMode
{
  /**
   * Round to the nearest integer. If the decimal part is 5, round to
   * the integer with the larger absolute value.
   *
   *  1.0  ->  1
   * -1.0  -> -1
   *  1.2  ->  1
   * -1.2  -> -1
   *  1.6  ->  2
   * -1.6  -> -2
   *  1.5  ->  2
   * -1.5  -> -2
   *  2.5  ->  3
   * -2.5  -> -3
   */
  case HalfAwayFromZero; // PHP_ROUND_HALF_UP
 
  /**
   * Round to the nearest integer. If the decimal part is 5, round to
   * the integer with the smaller absolute value.
   *
   *  1.0  ->  1
   * -1.0  -> -1
   *  1.2  ->  1
   * -1.2  -> -1
   *  1.6  ->  2
   * -1.6  -> -2
   *  1.5  ->  1
   * -1.5  -> -1
   *  2.5  ->  2
   * -2.5  -> -2
   */
  case HalfTowardsZero; // PHP_ROUND_HALF_DOWN
 
  /**
   * Round to the nearest integer. If the decimal part is 5, round to
   * the even integer.
   *
   *  1.0  ->  1
   * -1.0  -> -1
   *  1.2  ->  1
   * -1.2  -> -1
   *  1.6  ->  2
   * -1.6  -> -2
   *  1.5  ->  2
   * -1.5  -> -2
   *  2.5  ->  2
   * -2.5  -> -2
   */
  case HalfEven; // PHP_ROUND_HALF_EVEN
 
  /**
   * Round to the nearest integer. If the decimal part is 5, round to
   * the odd integer.
   *
   *  1.0  ->  1
   * -1.0  -> -1
   *  1.2  ->  1
   * -1.2  -> -1
   *  1.6  ->  2
   * -1.6  -> -2
   *  1.5  ->  1
   * -1.5  -> -1
   *  2.5  ->  3
   * -2.5  -> -3
   */
  case HalfOdd; // PHP_ROUND_HALF_ODD
 
  /**
   * Round to the nearest integer with a smaller or equal absolute value.
   *
   *  1.0  ->  1
   * -1.0  -> -1
   *  1.2  ->  1
   * -1.2  -> -1
   *  1.6  ->  1
   * -1.6  -> -1
   *  1.5  ->  1
   * -1.5  -> -1
   *  2.5  ->  2
   * -2.5  -> -2
   */
  case TowardsZero; // PHP_ROUND_TOWARD_ZERO
 
  /**
   * Round to the nearest integer with a greater or equal absolute value.
   *
   *  1.0  ->  1
   * -1.0  -> -1
   *  1.2  ->  2
   * -1.2  -> -2
   *  1.6  ->  2
   * -1.6  -> -2
   *  1.5  ->  2
   * -1.5  -> -2
   *  2.5  ->  3
   * -2.5  -> -3
   */
  case AwayFromZero; // PHP_ROUND_AWAY_FROM_ZERO
 
  /**
   * Round to the largest integer that is smaller or equal.
   * 
   *  1.0  ->  1
   * -1.0  -> -1
   *  1.2  ->  1
   * -1.2  -> -2
   *  1.6  ->  1
   * -1.6  -> -2
   *  1.5  ->  1
   * -1.5  -> -2
   *  2.5  ->  2
   * -2.5  -> -3
   */
  case NegativeInfinity; // PHP_ROUND_FLOOR
 
  /**
   * Round to the smallest integer that is greater or equal.
   * 
   *  1.0  ->  1
   * -1.0  -> -1
   *  1.2  ->  2
   * -1.2  -> -1
   *  1.6  ->  2
   * -1.6  -> -1
   *  1.5  ->  2
   * -1.5  -> -1
   *  2.5  ->  3
   * -2.5  -> -2
   */
  case PositiveInfinity; // PHP_ROUND_CEILING
}

The round() function will be updated to accept this new enum, while still supporting integer values to minimize breaking changes.

So, you can now use the round() function like so.

round(1.5, \RoundingMode::HalfAwayFromZero); // 2
round(1.5, \RoundingMode::HalfTowardsZero); // 2

The aim behind this change is to enhance the developer experience by making the code more intuitive and maintainable, with a smoother transition to the new enum-based system.

Read RFC

Raising zero to the power of negative number will give deprecation warning

Currently, when you raise zero to the power of a negative number, it will result into INF instead of throwing an exception.

var_dump(0 ** -1); //float(INF)
var_dump(0 ** -1.1); //float(INF)

But we already have the ability where if we divide a number with 0, it will throw a DivisionByZeroError exception.

And so, PHP 8.4 will address this inconsistency and will trigger a deprecation warning when you try to raise zero to the power of a negative number, with the intention of fully replacing this behavior with a DivisionByZeroError in PHP 9.0.

Read RFC

A new function to allow parsing of multipart/form-data content type for non-POST requests

PHP 8.4 introduces a new function called request_parse_body() to allow parsing of multipart/form-data content type for HTTP verbs other than POST, addressing the needs of RESTful APIs and improving performance for large data transfers.

This will extend the native parsing capabilities of PHP to support multipart/form-data requests for methods like PUT and PATCH, which are commonly used in RESTful APIs. This is currently only supported for POST requests.

#[Route('/api/videos', methods: ['PUT'])]
public function index(): Response {
    [$post, $files] = request_parse_body(options: [
        'post_max_size' => '128M',
    ]);
 
    // ...
}

The function enables userland code to parse such requests, providing flexibility and performance benefits, especially for handling large amounts of data. The function also allows for overriding global INI settings through an options parameter, offering endpoint-specific customization of parsing limits. This approach avoids potential security risks associated with global changes to PHP settings.

Read RFC

A dedicated class for stream processing

PHP 8.4 will introduce a dedicated StreamBucket class to replace the current stdClass object usage for stream processing, enhancing code clarity and IDE support, and deprecating the $bucket resource property and $datalen abbreviation in favor of $dataLength.

This change aims to address the current limitations where stream buckets are represented by generic stdClass objects, leading to less precise type handling and reduced IDE support.

Here’s how the new class will look like.

final class StreamBucket
{
    /**
     * @var resource
     * @deprecated after resource to object conversion happens
     */
    public $bucket;
    public string $data;

    /** @deprecated in PHP 8.5 or PHP 9.0 whichever comes next */
    public int $datalen;
    public int $dataLength;
}

The StreamBucket class will provide a clear structure with typed properties, which will facilitate better static analysis and autocompletion in development environments.

Read RFC

Session propagation will no longer be done using GET/POST requests

PHP 8.4 will be deprecating the use of GET/POST for session propagation and automatic URL transformation in PHP 8.4, with complete removal planned for PHP 9.0.

The PHP community is considering a proposal to deprecate two session handling features: the initialization of sessions using identifiers from GET/POST requests and the automatic transformation of URLs to include session IDs (use_trans_sid). These practices are deemed insecure and outdated, with cookies being the preferred method for session token propagation.

Essentially, the GET/POST methods for session propagation in PHP involve passing the session ID as part of the URL (in the case of GET) or within the body of a POST request. This will throw a deprecation warning if the following setting are used.

session.use_only_cookies=Off ; Will generate a deprecation warning
session.use_trans_sid=On ; Will generate a deprecation warning

This will encourage better security practices by phasing out support for less secure methods of session propagation.

Read RFC

A new function to efficiently calculate both the quotient and remainder in a single operation

PHP 8.4 will add a bcdivmod() function and a corresponding divmod() method to the BcMath\Number class to efficiently calculate both the quotient and remainder in a single operation.

The BCMath extension currently requires separate operations for division and modulus, which is inefficient. So, these functions will overcome this limitation.

/**  @return array{string, string} */
function bcdivmod(string $num1, string $num2, ?int $scale = null): array {}
 
/**  @return array{Number, Number} */
public function divmod(Number|string|int $num, ?int $scale = null, int $roundingMode = PHP_ROUND_HALF_UP): array {}

Here’s an example usage of the bcdivmod() function.

[$quot, $rem] = bcdivmod('123', '2');
 
// $quot is '61'
// $rem is '1'

And here’s an example usage of the divmod() method.

$slicesOfPizza = new BcMath\Number(8);
$mouthsToFeed = new BcMath\Number(3);
[$perMouth, $slicesLeft] = $slicesOfPizza->divmod($mouthsToFeed);
 
// $perMouth->value is '2'
// $slicesLeft->value is '2'

This change is inspired by similar functions in Python and Ruby and is expected to improve performance.

The new function and method are designed to return an array with the quotient and remainder, similar to the GMP extension’s gmp_div_qr() function.

Read RFC

Improvements to the XMLReader and XMLWriter classes

PHP 8.4 will be adding stream handling capabilities to XMLReader and XMLWriter classes to allow direct operation on already-open streams, enhancing efficiency and ease of use.

class XMLReader {
    /** @param resource $stream */
    public static function fromStream($stream, ?string $encoding = null, int $flags = 0, ?string $documentUri = null): static {}
}
 
class XMLWriter {
    /** @param resource $stream */
    public static function toStream($stream): static {}
}

This will address the limitation in XMLReader and XMLWriter classes that prevents them from operating on pre-existing open streams. This limitation often forces developers to use inefficient workarounds, such as loading entire streams into memory or writing to temporary files before processing.

Like I said previously, this will make it easy in environments where XML documents are too large to fit into memory comfortably, these functions allow for processing in chunks directly from a stream. This is particularly useful in server-side applications, such as parsing large configuration files or processing XML data feeds from external services enabling more efficient use of server resources.

Some extensions are going away from PHP core

PHP 8.4 will unbundle the ext/imap, ext/pspell, ext/oci8, and ext/PDO_OCI extensions from the PHP source distribution and move them to PECL for future maintenance and compatibility with PHP 8.4 and beyond.

This change would require PHP users to install these extensions from PECL if needed, as they will no longer be maintained by the PHP Core team.

Introduction of Lazy Objects

The implementation of lazy objects in PHP 8.4 to enable transparent lazy initialization at the engine level, improving performance and simplifying userland code for lazy loading patterns.

This will introduce two types of lazy objects—ghost objects and proxies—each with distinct initialization strategies:

• Ghost objects are initialized in-place.
• Proxies forward interactions to a separate instance.

The feature essentially will use the Reflection API to create and manage lazy objects, and specifies the behavior of these objects throughout their lifecycle, including initialization triggers, cloning, and handling of readonly properties and destructors by introducing new methods to the ReflectionClass and ReflectionProperty classes.

Creating Lazy Objects

Here is how you can create a lazy object for a class.

class MyClass
{
    public function __construct(private int $foo)
    {
        // Heavy initialization logic here.
    }
    
    // ...
}

// Initializer for a ghost object
$initializer = static function (MyClass $ghost): void {
    $ghost->__construct(123);
};

// Create a ReflectionClass instance for MyClass
$reflector = new ReflectionClass(MyClass::class);

// Create a lazy ghost object
$lazyGhost = $reflector->newLazyGhost($initializer);

// At this point, $lazyGhost is a lazy ghost object 
// that will be initialized when first used.

Handling the State of Lazy Objects

If you know certain properties ahead of time, you can set them without triggering initialization:

$reflector->getProperty('id')->setRawValueWithoutLazyInitialization($lazyGhost, 123);

Lifecycle of Lazy Objects

You can force the initialization of a lazy object using:

$initializedObject = $reflector->initializeLazyObject($lazyGhost);

A real-world usage of Lazy Objects

In a dependency injection container, you can defer the creation of expensive services until they are actually requested using lazy objects.

class ServiceContainer
{
    public function getService(string $serviceName)
    {
        if ($serviceName === 'expensiveService') {
            $reflector = new ReflectionClass(ExpensiveService::class);
            return $reflector->newLazyProxy(function () {
                // Expensive initialization logic
                return new ExpensiveService(); 
            });
        }
        
        // ...
    }
}

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