5

The PHP function in_array(...) "checks if a value exists in an array".

But I'm observing a very strange behavior on handling strings (PHP v7.0.3). This code

$needle = 'a';
$haystacks = [['a'], ['b'], [123], [0]];
foreach ($haystacks as $haystack) {
    $needleIsInHaystack = in_array($needle, $haystack);
    var_dump($needleIsInHaystack);
}

generates following output:

bool(true)
bool(false)
bool(false)
bool(true) <- WHAT?

The function returns true for every string $needle, if the $haystack contains an element with the value 0!

Is it really by design? Or is it a bug and should be reported?

automatix
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1 Answers1

13

If you do not set the third parameter of in_array to true, comparison is done using type coercion.

If the third parameter strict is set to TRUE then the in_array() function will also check the types of the needle in the haystack.

Under loose comparison rules, effectively 'a' is equal to 0 since (int)'a' == 0.

Matteo Tassinari
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  • Thank you for your answer! Yes, I didn't consider, that `'a' == 0` is `true`. – automatix Jul 28 '16 at 09:39
  • And it's even more crazy: While `'a' == 0` is `true`, `'1' == 0` IS `false` (because `(int) '1'` IS `1` and `1` IS NOT `0`). – automatix Jul 28 '16 at 12:23
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    `'a' == 0 IS TRUE`, `0 == null IS TRUE`, `null == 'a' IS FALSE`. If we replace the concrete values by variables, we'll see, that this behavior is illogical: `a = b`, `b = c`, `c <> a`. – automatix Jul 28 '16 at 12:48