AES Encryption/Decryption in PHP

AESEncrypt.php

<?php

declare(strict_types=1);

final class AESEncrypt
{
    private const CYPHER_ALGO = 'AES-256-CBC';

    public function __construct(private readonly string $passPhrase)
    {
    }

    public function encrypt(string $plainText): string
    {
        $ivSize = openssl_cipher_iv_length(self::CYPHER_ALGO);
        $iv = openssl_random_pseudo_bytes($ivSize);

        $cipherText = openssl_encrypt($plainText, self::CYPHER_ALGO, $this->passPhrase, OPENSSL_RAW_DATA, $iv);

        return base64_encode($iv . $cipherText);
    }

    public function decrypt(string $encryptedText): string
    {
        $data = base64_decode($encryptedText);

        $ivSize = openssl_cipher_iv_length(self::CYPHER_ALGO);
        $iv = mb_substr($data, 0, $ivSize, '8bit');
        $cipherText = mb_substr($data, $ivSize, null, '8bit');

        return openssl_decrypt($cipherText, self::CYPHER_ALGO, $this->passPhrase, OPENSSL_RAW_DATA, $iv);
    }
}