array_key_exists($key, $array) vs !empty($array[$key])

Question

I've seen a lot of people do the former, is there any performance benefit doing one vs the other? Or is it just an eye candy? I personally use the latter every time as it is shorter and personally more readable to me.

Note, both statements are not equal. If $array[$key] is "" or 0, it is empty but the key still exists. — Kaken Bok
– Kaken Bok, Commented Jul 30, 2011 at 16:58

KARASZI István · Accepted Answer · 2022-12-05 13:55:27Z

18

The other responses focus on the differences between the two functions. This is true, but if the source array does not contain null or 0 or "", ... (empty values) values you can benchmark the speed of the two functions:

<?php

function makeRandomArray( $length ) {
    $array = array();
    for ($i = 0; $i < $length; $i++) {
        $array[$i] = rand(1, $length);
    }

    return $array;
}

function benchmark( $count, $function ) {
    $start = microtime(true);
    for ($i = 0; $i < $count; $i++) {
        $function();
    }
    return microtime(true) - $start;
}

$runs = 100000;
$smallLength = 10;
$small = makeRandomArray($smallLength);

var_dump(benchmark($runs, function() {
    global $small, $smallLength;
    array_key_exists(rand(0, $smallLength), $small);
}));
var_dump(benchmark($runs, function() {
    global $small, $smallLength;
    !empty($small[rand(0, $smallLength)]);
}));

Which gave me the following results:

For a small array:

array_key_exists: float(0.18357992172241)
empty: float(0.072798013687134)
isset: float(0.070242881774902)

For a relative big array:

array_key_exists: float(0.57489585876465)
empty: float(0.0068421363830566)
isset: float(0.0069410800933838)

So if it's possible it's faster to use empty or isset.

Although, I would like to highlight that this is a micro-optimization and that most probably won't matter that much. You need to actually do proper profiling, to find where is the bottleneck in your application before you end up focusing on these small optimizations.

edited Dec 5, 2022 at 13:55

answered Jul 30, 2011 at 17:10

KARASZI István

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3 Comments

Yuri Over a year ago

array_key_exists, isset and empty behaves in a very different way. It shouldn't be a matter of performance only

xZero Over a year ago

Such performance difference is because isset() and empty() are language constructs while array_key_exists() is regular built-in function.

Pieter van den Ham Over a year ago

There is no performance difference (anymore) between array_key_exists and empty according to your code (PHP 8.1).

theking2 · Accepted Answer · 2024-02-04 12:55:34Z

array_key_exists($key, $array) and !empty($array[$key]) can produce different results therefore it is not a matter of performance or preference.

$array[$key]	array_key_exists($key, $array)	!empty($array[$key])
does not exist	false	false
is truthy	true	true
is falsey	true	false

You can see that the truth table is different for falsey values (false, 0, NULL, etc). Therefore !empty($array[$key]) is not suitable in situations where a falsey value could be considered present e.g. $array["number_of_children"] should not be tested for emptiness where the value 0 makes sense.

You can use isset($array[$key]) which produces results identical to array_key_exists($key, $array) with exactly one exception:

$array[$key]	array_key_exists($key, $array)	isset($array[$key])
does not exist	false	false
is truthy	true	true
is falsey but not NULL	true	true
is NULL	true	false

Yoshi · Accepted Answer · 2011-07-30 17:00:17Z

4

$array = array(
    'foo' => null
);

echo (int)!empty($array['foo']); // 0
echo (int)array_key_exists('foo', $array); // 1

answered Jul 30, 2011 at 17:00

Yoshi

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1 Comment

Gumbo Over a year ago

Same applies to isset: isset($array['foo']) will yield false.

Rahul · Accepted Answer · 2011-07-30 17:03:39Z

1

They both are different

array_key_exists($key, $array) checks whether the key exist in the array and returns TRUE if the given key is set in the array.

whereas

!empty($array[$key]) Determine whether a variable value is empty or not

answered Jul 30, 2011 at 17:03

Rahul

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