Home > PHP > Improve Performance of in_array()

When the array size is large, performance of the built-in function in_array() will be extremely poor. To solve this problem, we can implement a custom in_array() function using hash maps. Here is the source code:

$map = array();
foreach($a as $val) $map[$val] = 1;
function better_in_array($needle, $map) {
return isset($map[$needle]);
}

Let's compare the performance now:

$a = array();
for ($i=0; $i<100000; $i++) $a[$i]=uniqid(rand());

function better_in_array($needle, $map) {
return isset($map[$neddle]);
}

$ts = microtime(true);
for ($i=0; $i<1000; $i++) in_array($i, $a);
printf("in_array=%.4f\n", microtime(true) - $ts);

$ts = microtime(true);
$map = array();
foreach($a as $val) $map[$val] = 1;
for ($i=0; $i<1000; $i++) better_in_array($i, $map);
printf("better_in_array=%.4f\n", microtime(true) - $ts);

Result:

in_array=17.8276
better_in_array=0.0706



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