what is faster: in_array or isset? [closed]

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The answers so far are spot-on. Using isset in this case is faster because

  • It uses an O(1) hash search on the key whereas in_array must check every value until it finds a match.
  • Being an opcode, it has less overhead than calling the in_array built-in function.

These can be demonstrated by using an array with values (10,000 in the test below), forcing in_array to do more searching.

isset:    0.009623
in_array: 1.738441

This builds on Jason’s benchmark by filling in some random values and occasionally finding a value that exists in the array. All random, so beware that times will fluctuate.

$a = array();
for ($i = 0; $i < 10000; ++$i) {
    $v = rand(1, 1000000);
    $a[$v] = $v;
}
echo "Size: ", count($a), PHP_EOL;

$start = microtime( true );

for ($i = 0; $i < 10000; ++$i) {
    isset($a[rand(1, 1000000)]);
}

$total_time = microtime( true ) - $start;
echo "Total time: ", number_format($total_time, 6), PHP_EOL;

$start = microtime( true );

for ($i = 0; $i < 10000; ++$i) {
    in_array(rand(1, 1000000), $a);
}

$total_time = microtime( true ) - $start;
echo "Total time: ", number_format($total_time, 6), PHP_EOL;

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