while setting up mediawiki on my local development machine, the installer told me that since i do not have PECL extension to php installed, i will have to do with slower page load speeds with traditional php page loading.
Does PECL really increase page load speeds?
How do i install it on my Ubuntu LAMP server?
I can't answer as to why PECL will affect your page load times. But regarding the installation of PECL to your PHP installation Google is your friend.
I found this link How to install a PHP PECL extension/module on Ubuntu
Was the message you saw something like this?
"Warning: The intl PECL extension is not available to handle Unicode normalization, falling back to slow pure-PHP implementation. If you run a high-traffic site, you should read a little on Unicode normalization."
What it's telling you is that you should install the intl extension from PECL; otherwise MediaWiki will have to use its own Unicode normalization code, which is slow.
On Ubuntu, this extension is available as the php5-intl package.
sudo apt-get install php5-intl
for install on PHP 7.2 & Ubuntu 18.04 run this command:
sudo apt install php-intl