PHP 8 的性能提升主要來自新引入的 JIT 編譯器和 Zend 引擎優(yōu)化，但實(shí)際應(yīng)用中的收益因場景而異。1. JIT 編譯器在運(yùn)行時(shí)將部分代碼編譯為機(jī)器碼，顯著提升 CLI 腳本或長時(shí) API 的性能，但在短生命周期的 Web 請求中作用有限；2. OPcache 改進(jìn)增強(qiáng)了操作碼緩存和預(yù)加載功能，減少磁盤 I/O 和解析開銷，尤其利于 Laravel 或 Symfony 等框架；3. 多項(xiàng)內(nèi)部優(yōu)化如更高效的字符串和數(shù)組操作、更小的內(nèi)存占用等，雖每次提升微小但積少成多；4. 實(shí)際性能提升視應(yīng)用場景而定，在計(jì)算密集型任務(wù)中 PHP 8 可快 10–20%，但對于依賴數(shù)據(jù)庫或外部 API 的應(yīng)用則效果不明顯，盡管如此，升級至 PHP 8 仍值得，因其帶來更好的類型安全、語法改進(jìn)和未來兼容性。

PHP 8 brings several performance improvements over PHP 7, though the gains might not always be dramatic in real-world applications. The biggest changes come from under the hood — specifically, the introduction of a new JIT compiler and optimizations in the Zend Engine.

JIT Compilation: The Big New Feature

The most talked-about performance feature in PHP 8 is the Just-In-Time (JIT) compiler. While PHP has always been an interpreted language, JIT compiles parts of the code into native machine code at runtime, potentially reducing execution time.

• It's especially useful for long-running processes like CLI scripts or certain types of APIs.
• For traditional web requests (which are short-lived), the impact can be minimal because there's not enough time for JIT to really kick in.
• You can enable it by tweaking php.ini settings like opcache.jit_buffer_size and opcache.jit.

So while it sounds powerful, you won’t necessarily see a massive boost on every workload unless you're running something CPU-intensive.

Better Opcode Caching with OPcache Improvements

PHP 8 improves how OPcache handles compiled scripts, which leads to faster execution even without JIT.

• With better preloading support introduced in PHP 7.4 and refined in PHP 8, more classes and functions can be loaded once and reused across requests.
• This reduces disk I/O and parsing overhead, making each request slightly faster.
• Frameworks like Laravel or Symfony benefit significantly since they load many files per request.

If OPcache isn't enabled or configured properly, you might miss out on these benefits — so it’s worth checking your setup.

Smaller Optimizations Add Up

Beyond the big features, PHP 8 includes various internal optimizations that improve performance in subtle but meaningful ways.

• Match expressions, union types, and attributes may not directly affect speed, but they reduce boilerplate and unnecessary function calls.
• The engine uses less memory in some cases due to better handling of internal data structures.
• String handling and array operations have seen small but consistent improvements.

These changes might save only a millisecond or two per request, but when you’re serving thousands of requests per second, those milliseconds add up.

Real-World Performance Gains Vary

While benchmarks show PHP 8 being up to 10–20% faster than PHP 7 in some scenarios, actual results depend heavily on your application.

• If your app spends most of its time waiting on a database or external API, upgrading alone won’t magically make it faster.
• But if your app does heavy computations or runs in a long-running environment (like a custom server or worker process), PHP 8 can offer noticeable improvements.

In practice, moving to PHP 8 is still worth it — not just for raw performance, but also for better type safety, cleaner syntax, and future compatibility.

基本上就這些。

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