Req #79421 [Com]: foreach (array_keys($arr) as $k) is slow

Edit report at https://bugs.php.net/bug.php?id=79421&edit=1 ID: 79421 Comment by: michael dot vorisek at email dot cz Reported by: michael dot vorisek at email dot cz Summary: foreach (array_keys($arr) as $k) is slow Status: Open Type: Feature/Change Request Package: Performance problem PHP Version: 7.4.4 Block user comment: N Private report: N New Comment: As long as iterate thru the whole dataset, otherwise it can be orders of magnitude slower. $c = 20000; // create test array $arr = []; for ($i = 0; $i < 1000; $i++) { $arr[$i . 'x'] = $i . 'y'; // use sting keys, they may be slower than numeric ones } $t = microtime(true); for ($i = 0; $i < $c; $i++) { foreach ($arr as $k => $ignore) { $u = $k . '.'; // use key break; } } var_dump(round(microtime(true) - $t, 6)); $t = microtime(true); for ($i = 0; $i < $c; $i++) { foreach (array_keys($arr) as $k) { $u = $k . '.'; // use key break; } } var_dump(round(microtime(true) - $t, 6)); Previous Comments: ------------------------------------------------------------------------ [2020-04-10 07:00:55] alexinbeijing at gmail dot com Interestingly, benchmarking shows that the 2nd form of the code you show here is actually *slower* than the 1st. I don't know if foreach(array_keys(...) as ...) has already been optimized internally, but in any case, it doesn't seem that this suggested optimization is necessary. Recommend this ticket can be closed. ------------------------------------------------------------------------ [2020-03-27 19:50:24] michael dot vorisek at email dot cz Description: ------------ This is a feature request to optimize: foreach (array_keys($arr) as $k) {} instead of building array of keys optimize this in PHP internally to behave like: foreach ($arr as $k => $ignore) {} It is important to optimize it as foreach on keys is very commonly used. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=79421&edit=1