<?php
namespace ParagonIE\CipherSweet\Transformation;
use ParagonIE\ConstantTime\Binary;
use ParagonIE\CipherSweet\Contract\TransformationInterface;
/**
* Class LastFourDigits
* @package ParagonIE\CipherSweet\Transformation
*/
class LastFourDigits implements TransformationInterface
{
/**
* Returns the last 4 digits (e.g. for a social security or credit card
* number). If less then 4 digits are available, it will pad them with 0
* characters to the left.
*
* 1234567890 => 7890
* 123 => 0123
*
* @param string $input
* @return string
*/
public function __invoke($input)
{
$input = \preg_replace('/[^0-9]/', '', $input);
$input = \str_pad($input, 4, '0', STR_PAD_LEFT);
return Binary::safeSubstr($input, -4, 4);
}
}
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