How to call Ajax functions without onclick/onkeyup/onchange etc

I am trying to include a .php file that will generate a form for me by picking out questions from a MySQL database. I've found numerous ways to call this function that I have called getQuestions() with 1 parameter (page number). I've seen drop down menus that will execute my php file using onchange, or buttons (onclick) etc. But is there a way to use my function without these? I just want it to automatically load with the rest of the page without any unnecessary interactions.

Don't know if this matters but my page is made in jQuery Mobile so it should only be visible when the correct page/div-id is active.

function getQuestions(str)
    { 
    if (window.XMLHttpRequest)
      {// code for IE7+, Firefox, Chrome, Opera, Safari
      xmlhttp=new XMLHttpRequest();
      }
    else
      {// code for IE6, IE5
      xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
      }
    xmlhttp.onreadystatechange=function()
      {
      if (xmlhttp.readyState==4 && xmlhttp.status==200)
        {
            document.getElementById("page_1").innerHTML=xmlhttp.responseText;
        }
      }
    xmlhttp.open("GET","generate_questions.php?p="+str,true);
    xmlhttp.send();
    }

These are the functions I have tried to use to view the .php within the rest of the HTML (without success)

<script type="text/javascript">
                    $(document).ready(function() {
                    getQuestions(1);
                    });
                    </script>


window.onload = function() {
                    $("#page_1").load(getQuestions(1));
                    }

window.onload = function() {
                    getQuestions(1);
                    }

Seems I solved my problem by assigning the php code to a smaller div than originally planned. I can't assign it to the page id, but to a smaller div within the page. The odd thing is it seems I can't really generate new div's within the php code either, so that sort of limits it's usage.