Disabling Submit Button in PHP for Unauthorized User Group

I'm trying to figure out how to disable the submit button if the user is not part of a specific group, but I can only find examples for after the form is submitted. Can someone help out?

<button class="btn btn-primary" type="button" id="SubmitFileButton"> Submit </button>

Solution:

you get grup data in this page.you can get group data in this page then after you can write php condition in this button.

<button class="btn btn-primary" type="button" id="SubmitFileButton" <?php if(not part of group) disable; ?>> Submit </button>

Solution:

<button class="btn btn-primary" type="button" id="SubmitFileButton" disabled="disabled"> 
   Submit 
</button>

I assume that this is what you're looking for.