The release of PHP 8.0 has been a significant milestone in the world of PHP development. With a plethora of new features and performance improvements, it offers exciting opportunities for developers. However, like any major release, it also comes with its share of breaking changes. In this article, we’ll explore the most important breaking changes in PHP 8.0 and discuss how to adapt your code to the new version.

1. Upgrading to PHP 8.0

Before we dive into the breaking changes, it’s essential to understand the benefits of upgrading to PHP 8.0, which brings substantial performance improvements, new features, and enhanced syntax, making it a worthwhile upgrade for any PHP project. But, when making the transition, it’s crucial to be aware of potential compatibility issues, which we’ll address in detail in the following sections.

2. Deprecation and Removal of Deprecated Features

PHP 8.0 marks the end of the line for several deprecated features. If your code relies on these deprecated features, you will encounter issues when upgrading. Let’s look at some of the most notable deprecated features that have been removed in PHP 8.0.

a. Deprecation of ‘create_function’

In PHP 8.0, the create_function function has been deprecated. This function was used to create anonymous functions, but it had limitations and performance issues. Instead, you should use closures to achieve the same functionality.

Here’s how you might have used create_function:

$add = create_function('$a, $b', 'return $a + $b;'); 
echo $add(2, 3); // Output: 5


$add = function ($a, $b) {
return $a + $b;
echo $add(2, 3); // Output: 5

b. Deprecated ‘intl’ Functions

PHP 8.0 deprecated the ‘intl’ functions like transliterator_transliterate. These functions have been removed, and you should use the ‘Transliterator’ class instead.

Here’s how you might have used transliterator_transliterate:

$transliterated = transliterator_transliterate('Any-Latin; Latin-ASCII;', 'Héllo, Wörld');
echo $transliterated; // Output: Hello, World

Use the ‘Transliterator’ class instead:

$transliterator = Transliterator::create('Any-Latin; Latin-ASCII');
$transliterated = $transliterator->transliterate('Héllo, Wörld');
echo $transliterated; // Output: Hello, World

3. Changes in Function and Method Signatures

PHP 8.0 brings changes to function and method signatures, which can affect the compatibility of your code.

a. Mixed Type Declaration

In PHP 8.0, you can use the mixed type declaration. It’s a union type that allows any data type. This change is designed to improve type hinting flexibility. Here’s an example:

function foo(mixed $value): void {
// $value can be of any type

This is particularly useful when working with dynamic data that can have different types.

b. Union Types

PHP 8.0 introduces union types, which allow a parameter to accept multiple types. This can make your code more robust and expressive. For example:

function greet(string|int $name): string {
return "Hello, $name!";

In this example, the greet function can accept either a string or an integer as the name parameter.

c. Return Types

PHP 8.0 also introduces stronger return type declarations. You can now specify a return type as void or use union types for more flexibility.

function divide(int $a, int $b): int|float {
if ($b === 0) {
return INF; // Return type float
return $a / $b; // Return type int

These changes enhance the predictability of your code and make it easier to catch type-related errors at compile time.

4. New Syntax Features

PHP 8.0 brings several new syntax features that improve code readability and maintainability.

a. Match Expression

The match expression is a new and concise way to perform switch-like comparisons and return values based on a given input. It’s often considered a more elegant replacement for the traditional switch statement.

Here’s an example of using the match expression:

$color = 'red';

$result = match ($color) {
'red' => 'It's a red color.',
'blue' => 'It's a blue color.',
'green' => 'It's a green color.',
default => 'It's a different color.',

echo $result; // Output: It's a red color.

The match expression is especially useful when dealing with multiple conditions.

b. Named Arguments

PHP 8.0 introduces named arguments, allowing you to pass arguments to a function by specifying the parameter names. This improves code readability and makes it easier to work with functions that have many optional parameters.

Here’s an example:

function orderPizza($size, $toppings = [], $sauce = 'tomato') {
// Function logic here

// Using named arguments
orderPizza(size: 'large', toppings: ['pepperoni', 'mushrooms'], sauce: 'barbecue');

Named arguments make it clear which values correspond to which parameters, even when they are not provided in the same order as the function definition.

5. Error Handling and Exception Changes

PHP 8.0 introduces changes in error handling and exceptions that can enhance debugging and error reporting.

a. New Error Handling Functions

PHP 8.0 introduces new error handling functions like str_contains(), str_starts_with(), and str_ends_with(). These functions allow for more efficient and concise string manipulation.

Here’s an example:

if (str_contains('Hello, World', 'World')) {
echo 'Found it!';
} else {
echo 'Not found!';


These functions are designed to simplify common string-related tasks.

b. Throwable Interface

In PHP 8.0, all errors and exceptions implement the Throwable interface. This change allows for more consistent error handling and better integration with custom exception classes.

try {
// Code that may throw an exception
} catch (Throwable $e) {
// Handle the exception

This change simplifies the error handling process and makes it easier to work with different types of exceptions.

6. Performance Enhancements

One of the most exciting aspects of PHP 8.0 is its significant performance improvements. It’s faster and more efficient, thanks to the introduction of Just-In-Time (JIT) compilation. This means your PHP applications can run faster without any code changes. However, there are some best practices to consider to make the most of PHP 8.0’s performance enhancements.

a. OpCache Improvements

PHP 8+ brings improvements to OpCache, which is a bytecode cache that stores precompiled script bytecode in shared memory. It helps reduce script compilation time and improves the overall performance of your PHP applications. Ensure that OpCache is properly configured for your server to take advantage of these improvements.

b. Benchmarking and Profiling

To make the most of PHP 8.0’s performance enhancements, it’s crucial to benchmark and profile your applications. Tools like Xdebug and Blackfire can help you identify performance bottlenecks and optimize your code for PHP 8.0.

7. Tools and Resources for Migration

Migrating to PHP 8.0 can be a smooth process with the right tools and resources at your disposal. Here are some essential resources to help you with the migration:

a. Official PHP Migration Guide

The official PHP website provides a comprehensive migration guide that covers all breaking changes and their implications. This guide is a must-read for anyone planning to upgrade to PHP 8.0.

b. Static Analysis Tools

Static analysis tools like PHPStan and Psalm can help you identify potential issues in your code before you upgrade to PHP 8.0. These tools provide valuable insights into type-related errors and other compatibility issues.

c. Community Support

Online communities and forums like Stack Overflow and the PHP Reddit community are excellent places to seek help and advice during the migration process. Many experienced developers are willing to share their insights and solutions.

d. Composer and Dependency Management

Ensure that your project’s dependencies are compatible with PHP 8.0. Use Composer to manage your project’s dependencies and update them to versions that support PHP 8.0.

8. Testing and Debugging

Testing and debugging are crucial steps in the migration process. Here are some best practices:

a. Unit Tests

Review and update your unit tests to ensure they pass in PHP 8.0. Running your tests in different PHP versions can help identify potential issues.

b. Integration Tests

Test your application as a whole, focusing on its interaction with external services and databases. Ensure that all components work as expected in PHP 8.0.

c. Debugging Tools

Use debugging tools like Xdebug to identify and resolve issues during the migration. Xdebug can provide detailed information about code execution and variable values.

php 8.0
php 8.0


PHP 8.0 is a game-changer with its new features, enhanced performance, and improved syntax. While the breaking changes might require some adjustments, the benefits far outweigh the challenges. Embrace the new features and start the migration process today. With the right tools, resources, and best practices, you can take full advantage of PHP 8.0’s capabilities and ensure that your code runs smoothly in the latest version of PHP.

In conclusion, upgrading to PHP 8+ is a step forward in improving your PHP applications’ performance and maintainability. Understanding the breaking changes and how to adapt your code is essential for a successful migration. Stay informed, test rigorously, and enjoy the benefits of PHP 8.0.

Remember, change is an opportunity for growth, and PHP 8.0 is no exception.


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