You may see the following error when using the EWWW plugin:
EWWW Image Optimizer requires exec(). Your system administrator has disabled this function.
Why Is The Exec Function Disabled?
The exec() function in PHP allows your web server to directly execute other programs on the server. While this function may serve a legitimate use for some things, it's extremely risky.
The PHP exec() function is disabled on Pagely servers due to the extremely high risk of abuse. Even if you're using it for a legitimate purpose, an attacker could utilize this function in the event of a security hole inside a plugin or theme to cause quite a bit of damage.
To protect your site in the event that a plugin or theme that you're running becomes vulnerable to attack, disabling the exec() function limits the damage that can be done.
Can The Exec Function Be Enabled?
Due to the high risk that the exec() plugin poses to your site, we will not be able to enable it under any circumstances.
What Alternative Options Exist?
We recommend using API or cloud-based plugins where all the image processing happens on remote servers, and doesn't require any local executables to be installed.
There are few different plugins using this approach:
https://wordpress.org/plugins/ewww-image-optimizer-cloud/
https://wordpress.org/plugins/kraken-image-optimizer/
https://wordpress.org/plugins/wp-smushit/
https://wordpress.org/plugins/shortpixel-image-optimiser/
If you are on a VPS, we offer some flexibility and an alternative image processing service called Pressthumb. Please contact support for further assistance.