How can specific PHP parameters be modified?

It is possible de modify certain PHP parameters using directives inside an ".htaccess" file specific to your sites. To affect the whole site, lines of code can be added to a file that is named ".htaccess" (without the quotes) at the root of your website.

Therefore, if you need to change a specific parameter, such as max_input_vars, it is possible to add the following lines:

# PHP 8.1
<IfModule mod_php.c>
  php_value max_input_vars 10000
</IfModule>

# PHP 7.3
<IfModule mod_php7.c>
  php_value max_input_vars 10000
</IfModule>

To verify that the changes have taken effect, it is possible to verify on a page that outputs the PHP configuration information. You can, for example, create a page called "test.php" which contains the following lines:

<?php
  phpinfo();
?>

Certain content management systems provide such pages to ease that task. Check the documentation of your CMS to find out if such a page is available.