Php Fatal Error

Hello everyone.

I am using Plesk 12.0.18, Centos 7 and CSCart 4.3.4 for first time and PHP 5.6

The installer goes well but after that nothing works. I enable debug in frontend and I get this strange error

PHP Fatal Error


Class 'lessc' not found

Error at

app/Tygh/Less.php, line: 20


I install "php-lessphp" in Centos but nothing happens.

Can you help me?