CryptoJS.AES.encrypt to PHP - PHP implementation to Encrypt and decrypt a string compatible with crypto-js library AES default settings

CryptoJSAES.php

class CryptoJSAES
{
    public function encrypt($passphrase, $data, $salt = null): string
    {
        $salt = $salt ?: openssl_random_pseudo_bytes(8);
        [$key, $iv] = $this->_evpKDF($passphrase, $salt);
        $ct = openssl_encrypt($data, 'aes-256-cbc', $key, true, $iv);
        return $this->_encode($ct, $salt);
    }

    public function decrypt($passphrase, $base64): bool|string
    {
        [$ct, $salt] = $this->_decode($base64);
        [$key, $iv] = $this->_evpKDF($passphrase, $salt);
        return openssl_decrypt($ct, 'aes-256-cbc', $key, true, $iv);
    }

    private function _evpKDF($passphrase, $salt): array
    {
        $salted = '';
        $dx = '';
        while (strlen($salted) < 48) {
            $dx = md5($dx . $passphrase . $salt, true);
            $salted .= $dx;
        }
        $key = substr($salted, 0, 32);
        $iv = substr($salted, 32, 16);
        return [$key, $iv];
    }

    private function _decode($base64): array|string
    {
        $data = base64_decode($base64);
        if (!str_starts_with($data, 'Salted__')) {
            return '';
        }
        $salt = substr($data, 8, 8);
        $ct = substr($data, 16);
        return [$ct, $salt];
    }

    private function _encode($ct, $salt): string
    {
        return base64_encode('Salted__' . $salt . $ct);
    }
}