Toolbar, Privacy: Use array_key_first() to read the first key of an array

[mukeshpanchal27]

Summary

Replaces current( array_keys( $array ) ) with array_key_first( $array ) in the two places core uses that idiom.

current( array_keys( $a ) ) reads a single key, but gets there by materialising a brand-new array containing every key in $a, reading element 0 of that throwaway array, then discarding it. That is O(n) time plus O(n) memory to answer a question PHP can answer in O(1) — array_key_first() reads the first bucket of the hash table directly and allocates nothing.

array_key_first() is available in PHP 7.3 and later, below the current minimum supported version, so no polyfill is involved.

Benchmark

200,000 iterations per row, PHP 8.x:

Array size	current( array_keys( $a ) )	array_key_first( $a )	Speedup
5 keys	13.45 ms	7.15 ms	1.9x
20 keys	19.20 ms	7.12 ms	2.7x
100 keys	50.72 ms	7.10 ms	7.1x

The shape matters more than the absolute numbers: array_key_first() is flat regardless of array size, while current( array_keys() ) grows linearly with data that is never used.

Sites changed

File	Line	Note
src/wp-includes/admin-bar.php	1083	wp_admin_bar_new_content_menu() — runs on every admin page load and on every front-end load for logged-in users with the toolbar visible. $actions holds one entry per registered post type the user can create, so sites with many CPTs pay proportionally more.
src/wp-admin/includes/privacy-tools.php	77	_wp_personal_data_handle_actions() — the retry branch of the privacy request list table.

Behaviour

The two idioms differ in exactly one respect: on an empty array, current( array_keys( $a ) ) returns false while array_key_first( $a ) returns null. Both sites are safe:

• admin-bar.php — the function returns early ten lines above the change (if ( ! $actions ) { return; }), so $actions is guaranteed non-empty. The empty case is unreachable.
• privacy-tools.php — the value goes straight into absint(), and absint( false ) and absint( null ) both evaluate to 0. Identical result.

For every non-empty array both expressions return the same key with the same type. There is also no array-pointer side effect to preserve: current() was being applied to the temporary array returned by array_keys(), never to $actions itself.

Testing instructions

php -l src/wp-includes/admin-bar.php
php -l src/wp-admin/includes/privacy-tools.php
vendor/bin/phpcs src/wp-includes/admin-bar.php src/wp-admin/includes/privacy-tools.php
npm run test:php -- --filter '(adminBar|privacy)'

Results on this branch:

• php -l — no syntax errors in either file.
• phpcs — clean, 0 errors / 0 warnings.
• PHPUnit — OK (78 tests, 116 assertions).

Manually: load any admin screen as a user who can create posts and confirm the toolbar "New" node links to the same target as before.

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See Contributing to WordPress for more information.