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from wikipedia:

Most PHP accelerators work by caching the compiled bytecode of PHP scripts to avoid the overhead of parsing and compiling source code on each request (some or all of which may never even be executed). To further improve performance, the cached code is stored in shared memory and directly executed from there, minimizing the amount of slow disk reads and memory copying at runtime.

Just in time Compilation:

JIT compilers represent a hybrid approach, with translation occurring continuously, as with interpreters, but with caching of translated code to minimize performance degradation.

so is using PHP accelerators such as APC on PHP have equivalent implications towards performance with "Just-in-time" compiling PHP (assuming that it's possible to do so)....in fact are they actually the same thing?

Kuf
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user734027
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1 Answers1

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so is using PHP accelerators such as APC on PHP have equivalent implications towards performance with "Just-in-time" compiling PHP (assuming that it's possible to do so)....in fact are they actually the same thing?

Same concept, different execution.

When JIT is spoken of in most circles, it refers to compiling virtual machine bytecode into native bytecode. For example, Facebook's HHVM is a PHP implementation that uses a JIT engine.

However, PHP's native virtual machine doesn't do JIT to native bytecode. In fact, it doesn't do JIT at all in the traditional sense. While whole files are compiled to PHP bytecode on-demand, this isn't actually JIT.

Be careful with the term "PHP accelerator." Back in the PHP4 days, the bytecode created by the PHP parser could be optimized a bit to get better performance. This hasn't been needed since early PHP5. The only thing that APC, the Zend "Optimizer" and other "accelerator" products do to increase PHP performance is cache bytecode. The term "accelerator" should no longer be used to remove ambiguity.

If you're using standard PHP, then you do want a bytecode cache, just steer clear of products saying that they try to do PHP bytecode optimization.

Charles
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  • I know that is and old post, and maybe things have changed, but Zend optimizer+ does really optimize code. Quote: "In addition, it applies a few bytecode optimization patterns that make code execution faster.". https://github.com/zend-dev/ZendOptimizerPlus/ – XzKto Feb 22 '13 at 11:18
  • Yeah, it just happens that those optimizations made a much, *much* larger difference back in PHP4. Now that it's [proposed for inclusion in the core distribution](https://wiki.php.net/rfc/optimizerplus), it'll be interesting to see if the bytecode optimizations make any difference. – Charles Feb 22 '13 at 17:06
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    As of June, Facebook as release a PHP Jit compiler https://github.com/facebook/hiphop-php – Steven Jun 17 '13 at 23:41