Encrypting data with PHP, perhaps?

Question

PHP

Good afternoon!
The server has:
a certificate, a file with the .crt extension,
a private key file, a file with the .key
extension
And if necessary, decrypt it.
I almost do not understand this, tell me where to dig, please, can someone already do it?
I would be very happy with examples.
Thank you very much in advance!

Answer 1

php.net/manual/ru/function.openssl-encrypt.php
If for passwords, it's better to start from here:
php.net/manual/ru/faq.passwords.php#faq.passwords....