Php IF statement inside html in form validaiton

I'm trying to validate a form, and if empty would show an error that it is required. My problem is, even if i did not submitted a form yet, it already checks if the variable is empty. I need help.

here is the php above my html document

<?php

  if ($_SERVER['REQUEST_METHOD'] == "POST"){
    // The form has been submitted
    // We can do stuff here
        
        $email = $_POST['email'];
        $fname = $_POST['fname'];
        $lname = $_POST['lname'];
        $password = $_POST['password'];
        $password_confirm = $_POST['password_confirm'];
        
        
        if(empty($email) === true){
                
                        $error = 'Email address is required' ;
                
                }
        
  }
?>