What is max_input_vars? - max_input_vars is a setting in PHP that defines the maximum number of input variables that the server can process from an HTTP request, such as form data or URL parameters. This is important to maintain performance and prevent potential attacks. When the number of variables exceeds this limit, PHP may ignore the additional variables, which can cause problems for applications that expect to receive all the data. The default value is usually 1000, but may need to be increased occasionally.
Step 1: Log in to DirectAdmin (instructions).
Step 2: Click on Account Manager in the menu.
Step 3: Click on PHP Settings:

Step 4: In the section called Add New Override in the drop-down menu in the Settings row, select max_input_vars:

Step 5: In the Value line, set the value you need:

Step 6: Once you're done, the server will automatically remember your change.