Reduce the use of the `_wp_array_get()` function to improve performance

[aristath]

Merges work from Gutenberg to reduce significantly reduce the number of calls to _wp_array_get(), to improve performance.

This ticket merges the same changes from Gutenberg into Core, and applies the same logic where appropriate.

References:

• ​https://github.com/WordPress/gutenberg/pull/51116

This is a backport of ​https://github.com/WordPress/gutenberg/pull/51116 from Gutenberg

Trac ticket: https://core.trac.wordpress.org/ticket/59405

@aristath thanks for the PR. Could you please share the performance number before after the changes?

@aristath thanks for the PR. Could you please share the performance number before after the changes?

Trunk:

After this PR:

So on my test, we're saving 2582 call to the _wp_array_get() function, and 39ms.
These results are not accurate since XDebug does add a lot of overhead, but there is a clear improvement.

The coding standards disallow using the null coalescing operator right now, see https://core.trac.wordpress.org/ticket/58874

The coding standards disallow using the null coalescing operator right now, see https://core.trac.wordpress.org/ticket/58874

The coding standards do no such thing: ​https://developer.wordpress.org/coding-standards/wordpress-coding-standards/php/

The coding standards have no opinion on whether you use it or not. It's a matter of the minimum PHP version.

As for that Trac ticket: that's about whether to do a bulk update of the Core code base for it (and possibly enforce its use), which is a different matter.

Thank you @swissspidy 👍
Technically it's not "disallowed", it's just not used _yet_. If it was disallowed, tests would be failing.

Do you think it would be better if I change these to be isset() checks instead in this PR?
Do you believe that would that improve the readability of the code?

My bad, just glanced over it on mobike. Thanks for correcting me!

As this feels like a code qualiaty thing, I am going to ping @SergeyBiryukov

Rebased the PR, resolving conflicts 👍

@hellofromtonya if the use of ?? is considered a blocker in this PR, I can simply change it to isset() checks.
The performance improvements from this PR are the same regardless of which syntax we use, and the null coalescing operator is not the main point of this PR.

Would that help us move this ticket forward? We can convert isset() checks to ?? at a later date if we want.

Thank you all for the feedback!

I pushed a commit, changing the syntax so it doesn't use ?? anymore, and it now uses isset() checks. 👍

[SergeyBiryukov]

In 56709:

Editor: Reduce the use of the _wp_array_get() function to improve performance.

_wp_array_get() is an expensive function, and it's called thousands of times on each page view on the front end. While the function performance was slightly improved in #58376, it is still called more times than it should be.

This commit aims to further optimize its usage:

• In many cases, _wp_array_get() can be replaced with a much simpler and faster isset() check.
• The isset() function is capable of checking nested arrays, so isset( $foo['a']['b']['c'] ) will return false even if $foo['a'] is unset, without throwing any errors or warnings.
• When _wp_array_get() cannot be directly replaced with isset(), it would be good practice to wrap it in an isset() function so that _wp_array_get() only runs when it needs to.

Original PR from Gutenberg repository:

• ​#51116 Performance improvement: Reduce the use of the _wp_array_get() function

Follow-up to [55851], [56382].

Props aristath, jrf, spacedmonkey, mukesh27, swissspidy, hellofromTonya.
Fixes #59405.

Thanks for the PR! Merged in r56709.