How to use Class from .so file of PHP extension in Controller ?

What are you actually trying to do and load. What is the actual namespace.

step1.

pear install opendogs/mecab-beta

step2.

Test in PHP file.

<?php
$mecab = new \MeCab\Tagger();
$parsed = $mecab->parse('this is test');
var_dump($parsed);
?>

step1, step1 are all fine.

Problem is : how to use new \MeCab\Tagger(); in Laravel Controller ?

create a composer package (instead of using pear), and use composer to install it. Then it will show up in /vendor with the rest of your packages and what you wrote will work.

Did you try above leaving out the php tags, or appling a use statement: It should work in a controller just like you did:

$mecab = new \MeCab\Tagger();
$parsed = $mecab->parse('this is test');
var_dump($parsed);

It`s a PHP extension written in C, how to create composer package, please help

Or you could just require it, or https://stackoverflow.com/questions/21519919/composer-install-pear-package

I haven't checked myself but have you by chance looked at the pear site to see if they talk about installing their packages via composer.

It wouldn't hurt for you to check that yourself.