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Request #71239 Language construct for array_key_exists() (performance)
Submitted: 2015-12-29 17:24 UTC Modified: 2020-01-29 15:57 UTC
Avg. Score:5.0 ± 0.0
Reproduced:2 of 2 (100.0%)
Same Version:0 (0.0%)
Same OS:0 (0.0%)
From: andreas at dqxtech dot net Assigned: nikic (profile)
Status: Closed Package: Arrays related
PHP Version: 7.0.2RC1 OS:
Private report: No CVE-ID: None
 [2015-12-29 17:24 UTC] andreas at dqxtech dot net
There are places on the web telling me that array_key_exists($k, $a) is slower than isset($a[$k]).

Tests with PHP 5.5.9 confirm this, it seems that array_key_exists() uses almost 4x the time of isset().

On the other hand: Semantically, array_key_exists() is preferable over isset().
If you already know that $a is an array and not null, and that $k is a valid array key, then you don't want to have this tested again. You want TRUE or FALSE if the variables are set, and a warning (and FALSE, I guess) otherwise.

This allows the IDE to warn you if you test a variable that is possibly undefined, or possibly not an array. With isset(), the IDE will keep silent, which can lead to hidden bugs.

In theory, array_key_exists() should be faster than isset(), because there are fewer cases to consider.. but it is not, because one is a function and the other a "language construct".

Aside of that, there is of course the difference of how NULL values are handled.. In fact, in an ideal world, there would be two versions of array_key_exists(). Both with the performance of a language construct. But with a different behavior for NULL values.


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AllCommentsChangesGit/SVN commitsRelated reports
 [2018-08-23 00:49 UTC]
Related to Bug #71239
 [2018-08-23 00:50 UTC]
Related to Bug #76148
 [2020-01-29 15:57 UTC]
-Status: Open +Status: Closed -Assigned To: +Assigned To: nikic
 [2020-01-29 15:57 UTC]
array_key_exists() has an optimized opcode implementation since PHP 7.4.
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