PHP equivalent of $_GET for Javascript

getQueryVar.js

function getQueryVariable(variable,fromSrc) {
  fromSrc = fromSrc || false;
  if (fromSrc) {
    var myScript = document.currentScript;
    var query = myScript.src.replace(/^[^\?]+\??/,'');
  }
  else {
    var query = window.location.search.substring(1);
  }
  var vars = query.split('&');
  for (var i = 0; i < vars.length; i++) {
    var pair = vars[i].split('=');
    if (decodeURIComponent(pair[0]) == variable) {
      return decodeURIComponent(pair[1]);
    }
  }
  return null;
}