PHP

You need to grant write permissions for PHP on the following directory: /var/www/html/prestashop

3 STEP SOLUTION for PHP WRITE PERMISSIONS ISSUE CentOS 8 / RHEL 8 - NGINX / Prestashop
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Step 1: Determine PHP User

Create a PHP file containing the following:

<?php echo `whoami`; ?>
Upload it to your web server. The output should be similar to the following:

apache
  
Therefore, the PHP user is "apache" (or "www-data" in some cases)

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Step 2: Determine Owner of Directory

Next, check the details of the web directory via the command line:

ls -dl /var/www/example.com/public_html/example-folder
The result should be similar to the following:

drwxrwxr-x 2 exampleuser1 exampleuser2 4096 Mar 29 16:34 example-folder
Therefore, the owner of the directory is exampleuser1.
  
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Step 3: Change Directory Owner to PHP User

Afterwards, change the owner of the web directory to the PHP user:

sudo chown -R www-data /var/www/example.com/public_html/example-folder
Verify that the owner of the web directory has been changed:

ls -dl /var/www/example.com/public_html/example-folder
The result should be similar to the following:

drwxrwxr-x 2 www-data exampleuser2 4096 Mar 29 16:34 example-folder
Therefore, the owner of example-folder has successfully been changed to the PHP user: www-data.