Install PHP 8.0 Yaml extension on Ubuntu 18.04

I wrote a simple php based on the fisrt example. https://www.php.net/manual/es/function.yaml-parse.php I got...

Fatal error: Uncaught Error: Call to undefined function yaml_parse() in /var/www/html/p.php:33 Stack trace: #0 {main} thrown in /var/www/html/p.php on line 33

I use ondrej repository to install php.

root@hidra:~# cat /etc/apt/sources.list.d/ondrej-ubuntu-php-bionic.list 
deb http://ppa.launchpad.net/ondrej/php/ubuntu  bionic main
deb-src http://ppa.launchpad.net/ondrej/php/ubuntu  bionic main

There is no package to install yaml extension.

apt-file search phpize
apt-file search php8.0-yaml
apt-file search php8.2-yaml

Ok, let's try to compile it with phpize. There is not phpize either or php8.0-dev (In debian phpize ussualy is there)

root@hidra:~# apt-get install php8.0-dev
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package php8.0-dev
E: Couldn't find any package by glob 'php8.0-dev'
E: Couldn't find any package by regex 'php8.0-dev'

I tried with Ubuntu 22.04 too. The ondrej have no php8.x-dev php8.x-yaml. And php-dev o php-yaml try to install php7.2 versions. Besides, ymal code on PECL requires php 7. What would be the proper way to install it in these circumstances? I have used https://github.com/dallgoot/yaml to solve it, but I have curiosity with this issue.