php encryption - decryption algoritham

encrypt_decrypt('encrypt', 'set_encrypt_value_here');
encrypt_decrypt('decrypt', 'set_decrypt_value_here');
public static function encrypt_decrypt($action, $string)
{
    $output = false;

    $encrypt_method = "AES-256-CBC";
    $secret_key = ''; // set your key
    $secret_iv = ''; // set your key

    // hash
    $key = hash('sha256', $secret_key);

    $iv = substr(hash('sha256', $secret_iv), 0, 16);

    if ($action == 'encrypt'){
        $output = openssl_encrypt($string, $encrypt_method, $key, 0, $iv);
        $output = base64_encode($output);
    }
    if ($action == 'decrypt') {
        $output = openssl_decrypt(base64_decode($string), $encrypt_method, $key, 0, $iv);
    }

    return $output;
}