php8
一直以来，大家都在讨论 PHP 8 中是否会支持 JIT（Just-In-Time）即时编译执行功能，最新消息是官方已经确认将其引入。Include JIT into PHP 8?
Real nameYesNo
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Final result:502
https://wiki.php.net/rfc/jitPHP 实现了一个虚拟机 Zend VM，它会将人类可读脚本编译成虚拟机理解的指令，也就是操作码，这个执行阶段就是“编译时（Compile Time）”。在“运行时（Runtime）”执行阶段，虚拟机 Zend VM 会执行这些编译好的操作码。通常编译时与运行时两个阶段是独立分开的，脚本编译完成后，像 APC 与 OPCache 这样的字节码缓存组件会缓存这些操作码。而 JIT 去掉了编译时阶段，它将这编译时与运行时两个阶段合为一体，实现即时编译与执行。JIT 是一种编译器策略，它将代码表述为一种中间状态，在运行时将其转换为依赖于体系结构的机器码，并即时执行。在 PHP 中，这意味着 JIT 将为 Zend VM 生成的指令视为中间表述，并以依赖于体系结构的机器码执行，也就是说托管代码的不再是 Zend VM，而是更为底层的 CPU。虽然自 PHP 7.0 以来，通过优化核心数据结构 HashTable、强化 Zend VM 中某些操作码与持续改进 OPCache 的 Optimizer 组件等具体措施，PHP 性能得到了显著提升，但是实际上这些优化似乎已经走到极限了。现在 JIT 从底层着手，被认为是目前提升 PHP 性能的最佳出路。关于是否引入 JIT 的官方投票结果已于近日公布，因为大部分核心开发者投了赞成票，所以 PHP 8 中将会支持 JIT。另外值得一提的是，PHP JIT 对于使用 PHP 的网站来说提速可能并不明显，因为 JIT 在 CPU 密集型的代码上效果最好，而一般情况下，用 PHP 编写的程序都是 I/O 密集型的。简单来说就是，PHP 程序往往受限于 I/O 而不是 CPU，使 PHP 代码运行速度变慢的因素往往是它们正在执行的 I/O 操作，包括连接、读取和写入数据库、高速缓存、文件与套接字等。PHP 中 CPU 密集型代码的一个例子是 Zend/bench.php
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