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«Migrating websites from PHP7 to PHP8»

by Greg Lemmenmeier, posted on 8. June 2023 at 11:05, 424 Views

PHP 8, released in November 2020, brought several exciting features and improvements to the popular server-side scripting language. While it introduced enhancements in terms of performance, syntax, and error handling, it also presented some challenges for developers. In this blogpost, I will explore the problems associated with PHP 8 and discuss potential solutions to address them effectively.

I've migrated my own, rather complex website from PHP 7 to PHP 8.2 and everything works fine. It only took about 80 programming code amendments.

Backward Compatibility

One of the major challenges faced by developers with the release of PHP 8 is the issue of backward compatibility. PHP 8 introduced several backward-incompatible changes, meaning that code that worked perfectly fine in previous PHP versions may break when migrated to PHP 8. This poses a significant challenge for developers, especially when dealing with legacy codebases. The need to update or refactor large codebases to ensure compatibility can be time-consuming and resource-intensive.

Solution: To mitigate this challenge, developers should thoroughly review the migration guides and release notes provided by the PHP team. They should identify and address the backward-incompatible changes in their codebase before attempting to migrate to PHP 8. Additionally, utilizing tools like static analysis and automated testing can help identify potential issues early on and reduce the risk of breaking changes.

Third-Party Library Compatibility

Another problem with PHP 8 revolves around compatibility with third-party libraries and frameworks. Not all libraries and frameworks were updated to support PHP 8 immediately upon its release. This can create issues for developers who heavily rely on external packages and components in their projects. Incompatibility with PHP 8 can lead to runtime errors, deprecated function calls, or even complete failures.

Solution: When planning to migrate to PHP 8, it is crucial to assess the compatibility of the third-party libraries and frameworks used in the project. Check if the library maintainers have released PHP 8-compatible versions or if there are any known workarounds or alternative packages available. Engaging with the community, participating in forums, and keeping up with library updates can help developers stay informed and ensure a smoother transition.

Deprecated Features

PHP 8 introduced the deprecation of several features and functions that were deemed obsolete or inconsistent with the language's direction. While this is a positive step towards maintaining a cleaner and more consistent codebase, it can pose challenges for developers who have relied on these deprecated features extensively. Failure to address these deprecations can lead to potential bugs, security vulnerabilities, or unexpected behavior.

Solution: Developers should carefully review the list of deprecated features and functions provided in the PHP documentation. They should proactively identify the instances where deprecated features are used and update their code accordingly. It is recommended to replace deprecated functions with their recommended alternatives or utilize new features introduced in PHP 8 to achieve the desired functionality.

Performance Optimization

Although PHP 8 brings improvements in terms of performance and efficiency, it also presents challenges in optimizing existing codebases. Some code patterns that were considered performant in previous versions of PHP may not yield the same results in PHP 8. This means that developers need to reassess and potentially refactor their code to take advantage of the optimizations provided by PHP 8.

Solution: Developers should analyze their codebase to identify performance bottlenecks and areas that could benefit from PHP 8 optimizations. Utilizing PHP 8's new features like the Just-in-Time (JIT) compiler, named arguments, or attributes can help improve performance in specific scenarios. Profiling tools, benchmarking, and load testing can assist in identifying areas that need optimization and measuring the impact of changes made.

Step 1: Verify compatibility

Before beginning the migration process, it's essential to ensure that your existing codebase is compatible with PHP 8. Several tools can help you assess compatibility, such as the PHP Compatibility Checker. This tool scans your PHP files and flags any potential issues that may arise during the migration. Take note of the reported problems and address them accordingly to make your code compatible with PHP 8.

Step 2: Update dependencies

Next, it's crucial to update all the dependencies and libraries used by your website to their PHP 8-compatible versions. Check the documentation of each library you rely on to identify any breaking changes or updates required. Update your composer.json or package.json file accordingly to fetch the compatible versions of the dependencies.

Step 3: Deprecated Features

PHP 8 introduced several features and functions that have been deprecated, meaning they are no longer recommended and will be removed in future versions. Scan your codebase for any usage of deprecated features and replace them with their recommended alternatives. Here are a few common examples:

Deprecated: preg_replace('/pattern/e', $replacement, $subject);
Replace with: preg_replace_callback('/pattern/', function($matches) use ($replacement) { return $replacement; }, $subject);

Deprecated: assert($condition, $message);
Replace with: if (!$condition) { throw new \AssertionError($message); }

Deprecated: $array[] = 'value';
Replace with: array_push($array, 'value');

Make sure to thoroughly review the PHP manual and changelog for other deprecated features specific to your codebase and replace them accordingly.

Step 4: Type Declarations

PHP 8 introduced stricter type checking and enhanced type declaration features. To fully leverage these improvements, update your codebase to use the new type declaration syntax. Type declarations help enforce strong typing, leading to improved code quality and better error handling.

In addition to type declarations, PHP 8 also introduced union types, allowing you to specify multiple possible types for a parameter or return value. This flexibility can be particularly useful when dealing with dynamic data.

For example:
function processValue(int|string $value): void {
// Code to handle the value

Step 5: Error Handling

PHP 8 introduced a new Throwable interface that acts as the base interface for all exceptions and errors. Update your codebase to utilize this new interface for exception handling. This change helps streamline error management and makes it easier to handle different types of exceptions uniformly.

Before PHP 8:
try {
// Code that may throw an exception }
catch (Exception $e) {
// Handle the exception

After PHP 8:
try {
// Code that may throw an exception }
catch (Throwable $e) {
// Handle the exception

By catching the Throwable interface, you ensure your exception handling is future-proof and compatible with PHP 8 and beyond.

Step 6: Testing and Debugging

After making the necessary changes, it's crucial to thoroughly test your website to ensure that everything is functioning correctly. Automated tests can help identify any regressions or issues introduced during the migration process. Update your test suites to reflect the changes made and ensure they cover critical functionality.

Additionally, debugging tools such as Xdebug can be invaluable in pinpointing and resolving any issues that arise during the migration. Set up Xdebug with your PHP 8 environment and take advantage of its features like breakpoints, stack tracing, and variable inspection to diagnose and fix any bugs or compatibility issues.

Performance Comparison

Sorting algorithms play a crucial role in various programming scenarios. Among them, Bubble Sort is a simple and intuitive algorithm used to sort arrays. With the release of PHP 8, developers have gained access to numerous performance improvements.

Bubble Sort is a straightforward sorting algorithm that repeatedly steps through an array, compares adjacent elements, and swaps them if they are in the wrong order. The process continues until the entire array is sorted. While Bubble Sort is not the most efficient algorithm for large datasets, it serves as an excellent example for performance comparison.

Let's begin by looking at a simple Bubble Sort implementation in PHP 7 which I would program as follows:

function bubbleSort(array $arr): array {
$n = count($arr);
for ($i = 0; $i < $n - 1; $i++) {
for ($j = 0; $j < $n - $i - 1; $j++) {
if ($arr[$j] > $arr[$j + 1]) {
$temp = $arr[$j];
$arr[$j] = $arr[$j + 1];
$arr[$j + 1] = $temp;
return $arr;

Now, let's see how the same Bubble Sort algorithm can be implemented in PHP 8:

function bubbleSort(array $arr): array {
$n = count($arr);
for ($i = 0; $i < $n - 1; $i++) {
$swapped = false;
for ($j = 0; $j < $n - $i - 1; $j++) {
if ($arr[$j] > $arr[$j + 1]) {
[$arr[$j], $arr[$j + 1]] = [$arr[$j + 1], $arr[$j]];
$swapped = true;
if (!$swapped) {
return $arr;

To measure the performance of Bubble Sort in PHP 7 and PHP 8, we will use an array with 10,000 random elements.

$randomArray = [];
for ($i = 0; $i < 10000; $i++) {
$randomArray[] = mt_rand(1, 10000);

Using the microtime() function, we can compare the execution times of Bubble Sort in both versions:

// Bubble Sort in PHP 7
$start = microtime(true);
$result7 = bubbleSort($randomArray);
$time7 = microtime(true) - $start;

// Bubble Sort in PHP 8
$start = microtime(true);
$result8 = bubbleSort($randomArray);
$time8 = microtime(true) - $start;

echo "Execution time in PHP 7: " . $time7 . " seconds\n";
echo "Execution time in PHP 8: " . $time8 . " seconds\n";

After running the code, we obtain the execution times of Bubble Sort in PHP 7 and PHP 8. The results may vary depending on your system, but generally, PHP 8 demonstrates *significant* performance improvements over PHP 7.

In Summary

Migrating your website from PHP 7 to PHP 8 offers numerous benefits, including improved performance, enhanced security, and access to new features. By following the steps outlined in this blogpost and addressing the necessary code changes, you can successfully migrate your website to object-oriented PHP 8. Remember to thoroughly test your website and keep an eye out for potential compatibility issues during and after the migration process. With careful planning and attention to detail, you can leverage the power of PHP 8 to enhance your website's performance and functionality.

• Posted on 8. June 2023 at 11:05     ▶ 424 Views     ≡ Category: Web Development

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