Resolved WP-Optimize WebP Shell Functions

[PeterH]

Server operating system version

Ubuntu 22.04

Plesk version and microupdate number

18.0.59 #2

I have installed the WordPress WP-Optimize plugin but when I check the option "Create WebP version of image" I get the following error:

Required WebP shell functions are not available on server

Can anyone tell me what this error message means and how I can resolve it?

 

[PeterH]

I had disabled a number of PHP functions on the advice of a security tutorial and it turns out that the following functions are necessary to create a WebP version of the image:

passthru
shell_exec
system
proc_open


After I enabled these features again, it worked without any problems.