composer require wilkques/pkce-php
use Wilkques\PKCE\Generator;
$codeVerifier = Generator::codeVerifier();
$codeChallenge = Generator::codeChallenge($codeVerifier);
// or
$pkce = Generator::generate();
$codeVerifier = $pkce->getCodeVerifier();
$codeChallenge = $pkce->getCodeChallenge();
// or
$codeVerifier = $pkce->codeVerifier;
$codeChallenge = $pkce->codeChallenge;
// or
$pkce->toArray(); // output ['codeVerifier' => '123', 'codeChallenge' => '456']
$pkce->toJson(); // output {'codeVerifier' : '123', 'codeChallenge' : '456'}