What does this error mean after calling the openssl_encrypt function?

Question

When calling the function openssl_encrypt, always returned false. When checking the function openssl_error_string, I get the following error:

error:0906D06C:PEM routines:Pem_read_bio:no start line

The code I’m doing the tests is this:

$data = 'Olá, Wallace!';

$encryption_key = openssl_random_pseudo_bytes(32);

$iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('AES-256-CBC'));

$encrypted = openssl_encrypt($data, 'AES-256-CBC', $encryption_key, 0, $iv);

if (false === $encrypted) {

    var_dump(openssl_error_string());

    exit;
}

Why this error is generated?

I’m doing these tests trying to find a solution to this question:

/questions/185919/erro-de-encryption%C3%A7%C3%A3o-no-Laravel-ap%C3%B3s-actualize%C3%A7%C3%A3o-do-php-could-not-Encrypt-the-d