matching openssl's enc ciphers to php's openssl functions' ciphers: where's "chacha20-poly1305"?

[PGNet Dev]

I'm deploying a php app that makes use of php's openssl functions

	https://www.php.net/manual/en/ref.openssl.php

atm, I've

	php -v
		PHP 7.4.8 (cli) (built: Jul  9 2020 08:57:23) ( NTS )
	openssl version
		OpenSSL 1.1.1g FIPS  21 Apr 2020

The php app config defaults to an encryption method of

	$config['cipher_method'] = 'DES-EDE3-CBC';

for encrypting a session pwd,

	This key is used to encrypt the users imap password which is stored
	in the session record. 

I'd like to change that to a CHACHA20 variant.

As listed by 

	https://www.php.net/manual/en/function.openssl-get-cipher-methods.php

the list of php-supported openssl ciphers includes

    [92] => chacha20
    [93] => chacha20-poly1305

double checking available encryption ciphers @ openssl

	openssl enc -ciphers

only lists

	-chacha20

not the add'l,

	-chacha20-poly1305

why is this^^ variant not shown?

am I comparing apples & oranges here, looking at the wrong lists?

perhaps just aliases for a singular cipher?