"QXcbConnection: Could not connect to display:1" when running xvfb CuteCapt from PHP

Thank you for your help.
I'm a new server user who recently started using Linux.

Capturing web pages (specifying URLs, rendering, and saving images) is a trial and error process. You can even install "CuteCapt" and its association in CentOS 6 to run on SSH.

The command succeeds with the following

xvfb-run --auto-servernum --server-num=1CuteCapt --url=https://www.google.co.jp/ --out=/var/www/html/capture/Google.jpg

You would like to run this command from PHP.
(I have quite a history of PHP, but I have no experience of hitting commands outside, so I'm trying to guess...)

$res=exec(escapeshellcmd('xvfb-run --auto-servernum --server-num=1CuteCapt --url=https://www.google.co.jp/ --out=/var/www/html/capture/Google.jpg'));

I just put it in and found out that $res is

QXcbConnection:Could not connect to display:1

contains and no images are generated.

I understand that there is a moss around the connection to the virtual display.

I don't understand why a successful SSH command fails when I run it in PHP. I don't know what to try next, so I'm on the rocks.

It may be a rudimentary misunderstanding or mistake, but
Thank you for your advice