What's quicker and better to determine if an array key exists in PHP?

alex_31671 0
Viewed 137338

Consider these 2 examples...

$key = 'jim';

// example 1
if (isset($array[$key])) {
    // ...
}

// example 2    
if (array_key_exists($key, $array)) {
    // ...
}

I'm interested in knowing if either of these are better. I've always used the first, but have seen a lot of people use the second example on this site.

So, which is better? Faster? Clearer intent?

php performance
11 Answers

isset() is faster, but it's not the same as array_key_exists().

array_key_exists() purely checks if the key exists, even if the value is NULL.

Whereas isset() will return false if the key exist and value is NULL.

user_368050

With Php 7 gives the possibility to use the Null Coalescing Operator.

The null coalescing operator (??) has been added as syntactic sugar for the common case of needing to use a ternary in conjunction with isset(). It returns its first operand if it exists and is not NULL; otherwise it returns its second operand.

So now you can assign a default value in case the value is null or if the key does not exist :

$var = $array[$key] ?? 'default value'
user_25196310

Well, the main difference is that isset() will not return true for array keys that correspond to a null value, while array_key_exists() does.

Running a small benchmark shows that isset() it's faster but it may not be entirely accurate.

CMS_54450

there is a difference from php.net you'll read:

isset() does not return TRUE for array keys that correspond to a NULL value, while array_key_exists() does.

A very informal test shows array_key_exists() to be about 2.5 times slower than isset()

Scott_Evernden_113970

As to "faster": Try it (my money is on array_key_exists(), but I can't try it right now).

As to "clearer in the intent": array_key_exists()

Tomalak_187710

Obviously the second example is clearer in intent, there's no question about it. To figure out what example #1 does, you need to be familiar with PHP's variable initialization idiosyncracies - and then you'll find out that it functions differently for null values, and so on.

As to which is faster - I don't intend to speculate - run either in a tight loop a few hundred thousand times on your PHP version and you'll find out :)

moocha_144440

I wanted to add that you can also use isset to search an array with unique elements. It is lot faster than using in_array, array_search or array_key_exists. You can just flip the array using array_flip and use isset to check if value exists in the array.

<?php

$numbers = [];
for ($i = 0; $i < 1000000; $i++) {
    $numbers[] = random_int("9000000000", "9999999999");
}

function evaluatePerformance($name, $callback)
{
    global $numbers;
    $timeStart = microtime(true);

    $result = $callback("1234567890", $numbers) ? 'true' : 'false';

    $timeEnd = microtime(true);
    $executionTime =  number_format($timeEnd - $timeStart, 9);

    echo  "{$name} result is {$result} and it took {$executionTime} seconds. <br>";
}

// Took 0.038895845 seconds.
evaluatePerformance("in_array", function ($needle, $haystack) {
    return in_array($needle, $haystack);
});

// Took 0.035454988 seconds.
evaluatePerformance("array_search", function ($needle, $haystack) {
    return array_search($needle, $haystack);
});

$numbers = array_flip($numbers);

// Took 0.000024080 seconds.
evaluatePerformance("array_key_exists", function ($needle, $haystack) {
    return array_key_exists($needle, $haystack);
});

// Took 0.000013113 seconds.
evaluatePerformance("isset", function ($needle, $haystack) {
    return isset($haystack[$needle]);
});
user_12735500
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