Cache

Cache, or caching, is a technique used to store and reuse the results of expensive operations to improve performance.

There are different types of caches, depending on where they are applied: opcode cache, data cache, query cache, etc.

<?php

$count = count($array);
// $count is a cache for the number of elements in the array
// it saves a call to count() for every loop

for($i = 0; $i < $count; ++$i) {
     doSomething($i);
}

?>

Documentation

See also PHP cache

Related : Memoization