Verify an Argon2 Password with a Secret and Memory Guard

Demonstrates Crypt2.Argon2VerifyPassword when the hash was created with a secret (pepper) or ad, and the use of maxMemoryKb to guard against untrusted hash strings.

<?php

use Chilkat2\Crypt2;
use Chilkat2\JsonObject;

$crypt = new Crypt2();

// The password should come from a secure source rather than being hard-coded.
$password = 'correct horse battery staple';

$phcHash = '$argon2id$v=19$m=131072,t=4,p=2$c29tZXJhbmRvbXNhbHQ$3fJ7v1qKcVJ0lHqXjBQZ8mYm3sNTfSPRt0bqDl9kEyM';

// When the hash was created with a secret (pepper) or ad, the same values must be supplied to verify.
// Only the secret, ad, encoding, passwordCharset, and maxMemoryKb members of the options are used;
// everything else is ignored.
$json = new JsonObject();
$json->UpdateString('secret', 'application-wide-pepper');
$json->UpdateString('secretEncoding', 'utf-8');

// maxMemoryKb guards against a hash from an untrusted source claiming an enormous memory cost.  The
// memory cost is taken from the hash string, so this limit is checked before any memory is allocated.
// It defaults to 2 GB.
$json->UpdateInt('maxMemoryKb', 262144);

// Argon2VerifyPassword returns 1 if the password matched, 0 if it did not match, and -1 if the
// verification could not be performed.  Always test for a match with == 1.
$verifyResult = $crypt->Argon2VerifyPassword($password, $json->Emit(), $phcHash);
if ($verifyResult == 1) {
    echo "The password is verified.\n";
} else {
    if ($verifyResult == 0) {
        echo "The password does not match.\n";
    } else {
        echo 'The verification could not be performed: ', $crypt->LastErrorText, "\n";
    }
}