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Polyfill Laravel Package
symfony/polyfill
Symfony Polyfill backports newer PHP features and provides compatibility layers for missing extensions and functions, helping apps run across different PHP versions and configurations. It covers utilities like str_contains, array_key_first, mbstring/iconv, intl classes, UUID, and many PHP 7.2–8.x co...
PHP polyfills
Frequently asked questions about Polyfill
- How do I install Symfony Polyfill in a Laravel app?
- Install it with Composer using composer require symfony/polyfill for the umbrella package or a targeted package such as symfony/polyfill-php80. Laravel does not need a service provider because the polyfills are autoloaded functions and classes. In most Laravel projects the polyfills arrive transitively through Symfony components or other dependencies. Install only the specific polyfills you need to keep vendor/ lean.
- Which Symfony polyfill do I need for str_contains in Laravel?
- Use symfony/polyfill-php80, which backports str_contains, str_starts_with, str_ends_with, and related PHP 8.0 features. It defines the functions only when they are not natively available, so it is safe on PHP 8.0 and newer. If Laravel or another dependency already requires it, Composer may have installed it without an explicit require.
- Does Symfony Polyfill work with Laravel 10 and Laravel 11?
- Yes, Symfony Polyfill is framework-agnostic and works through Composer autoloading in Laravel 10, Laravel 11, and older supported versions. Laravel 10+ requires PHP 8.1 or newer, so many PHP-version polyfills become unnecessary. You may still need extension polyfills such as mbstring or intl on servers where those extensions are disabled. Audit composer.json and prune unused polyfills after upgrades.
- Can Symfony Polyfill let my Laravel app run on PHP 7.4 or older?
- Targeted polyfills can backport newer functions and classes such as str_contains, array_key_first, JsonException, and ValueError to older PHP runtimes. They do not add newer language syntax, so your Laravel code and dependencies must still parse on the installed PHP version. Polyfills are most useful when a package uses newer functions but the server runs an older PHP branch. Plan a real PHP upgrade rather than relying on polyfills indefinitely.
- What happens if mbstring or intl extension is missing on the server?
- symfony/polyfill-mbstring provides fallbacks for mb_* functions, and the symfony/polyfill-intl-* packages provide limited intl class and function replacements. These fallbacks keep Laravel string, validation, and localization code working when extensions are missing. Native extensions are faster and more complete, especially for non-English locales and heavy multibyte processing. Enable the real extensions in production when possible.
- Is Symfony Polyfill a performance problem for high-traffic Laravel apps?
- The package is lightweight and loads fallback code only when the native function or class is missing. On PHP versions and servers with the native features available, there is effectively no runtime overhead. Missing-extension polyfills like mbstring can be slower than the real extension under heavy use. Use Composer replace to drop unneeded polyfills after PHP upgrades and monitor performance in production.
- How do I remove Symfony polyfills after upgrading PHP in Laravel?
- Audit which polyfills are installed with composer show and composer why symfony/polyfill-php80. After upgrading PHP, add replace entries in your root composer.json for the specific symfony/polyfill-* packages that are no longer needed. Composer will then satisfy transitive requirements without installing those packages. Run the full Laravel test suite before deploying because a dependency may rely on a polyfilled edge case.
- Is Symfony Polyfill safe for production and actively maintained?
- Symfony Polyfill is MIT licensed and maintained by the Symfony team with regular releases and testing against native PHP behavior. Security issues are handled through Symfony's advisory process, including patched CVEs. For production, pin to maintained versions and monitor Composer audit or Symfony security advisories. It is widely used by Symfony components and Laravel dependencies, so the maintenance risk is low.
- Do Symfony polyfills conflict with native PHP extensions?
- No, polyfills guard definitions with function_exists or class_exists checks and defer to native PHP when the feature or extension is present. That makes them safe alongside real mbstring, intl, or ctype extensions. Be aware that some polyfills are intentionally limited, such as intl classes supporting only the en locale. Test locale-specific and multibyte edge cases if you depend on fallback behavior.
- What are alternatives to Symfony Polyfill for Laravel compatibility?
- The main alternatives are upgrading to a newer PHP version, enabling the missing native extension, or using narrower test-only helpers such as phpunit/phpunit-polyfills. Symfony Polyfill remains the standard Composer-based compatibility layer used across the Symfony and Laravel ecosystems. Choose targeted polyfills rather than the umbrella package when you only need one feature. Always verify behavior against native PHP in CI.
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