<?php
declare(strict_types=1);
namespace Pelago\Emogrifier\Utilities;
/**
* When computing many array intersections using the same array, it is more efficient to use `array_flip()` first and
* then `array_intersect_key()`, than `array_intersect()`. See the discussion at
* {@link https://stackoverflow.com/questions/6329211/php-array-intersect-efficiency Stack Overflow} for more
* information.
*
* Of course, this is only possible if the arrays contain integer or string values, and either don't contain duplicates,
* or that fact that duplicates will be removed does not matter.
*
* This class takes care of the detail.
*
* @internal
*/
class ArrayIntersector
{
/**
* the array with which the object was constructed, with all its keys exchanged with their associated values
*
* @var array<array-key, array-key>
*/
private $invertedArray;
/**
* Constructs the object with the array that will be reused for many intersection computations.
*
* @param array<array-key, array-key> $array
*/
public function __construct(array $array)
{
$this->invertedArray = \array_flip($array);
}
/**
* Computes the intersection of `$array` and the array with which this object was constructed.
*
* @param array<array-key, array-key> $array
*
* @return array<array-key, array-key>
* Returns an array containing all of the values in `$array` whose values exist in the array
* with which this object was constructed. Note that keys are preserved, order is maintained, but
* duplicates are removed.
*/
public function intersectWith(array $array): array
{
$invertedArray = \array_flip($array);
$invertedIntersection = \array_intersect_key($invertedArray, $this->invertedArray);
return \array_flip($invertedIntersection);
}
}