php - JavaScript disabled on Firefox meaning my buttons don't work, is there a way to write the buttons such that they will work?

So I have written a basic page which has buttons:

with the script:

function minus() {
  if ( > 1){
  var num =  - 1;
  var number=num;
  window.location.href = "page2.php?w1=" + number;}

};

So this just subtracts 1 off of a PHP variable and it works perfectly well in Chrome, IE and Safari, but in Firefox it doesn't work at all. Is this a security thing is this code particularly insecure?.

Is there any way in which I can write a button to change this PHP variable without using JavaScript as to make it work on Chrome, IE, Safari + Firefox?

Many thanks