in_array() performance optimization

Question

I have the following condition:

if(in_array($needle, $haystack) ||
    in_array($needle . "somePostfix", $haystack) ||
    in_array($needle . "someOtherPostfix", $haystack) ||
    // and some more) {
    // do something
}

My haystack contains more than 10k elements, and this check takes about 400ms. I know that in_array has to iterate over the whole array multiple times. In my case the common case is that the element is not found. and I tried to improve this by creating the following method that only iterates once over the haystack:

function wildcardInArray($needle, $haystack) {
    foreach ($haystack as $value) {
        if (true === fnmatch($needle . '*', $haystack)) {
            return true;
        }
    }
    return false;
}

But this decreases my performance even more, seems to me that fnmatch is the bottleneck.

Is there any improvement for this case of array search?

Answer 1

You can use your array as 'keys', i.e:

$arr = ['a', 'b', 'c', … ]; to $arr = ['a' => true, 'b' => true, …].

You will consume more memory but you will have an instant result with isset($arr[$key]);.

Fastest but biggest in memory, you can use stdClass and isset($obj->$key);

$obj = new stdClass();
$obj->{'a'} = true;
$obj->{'b'} = true;
$obj->{'…'} = true;

If you can't change your array structure, tell us if you can sort manually the array contents?

// generic
$length = strlen($needle);
$char = $needle[0];
$found = false;
$suffixes = [ false, 'somePostfix', 'someOtherPostfix' ];

foreach($haystack as $entry) {
  if ($char === $entry[0] && $needle === substr($entry, 0, $length)) {
    $suffix = substr($entry, $length);
    if (in_array($suffix, $suffixes, true)) {
      $found = true;
      break;
    }
  }
}