php - Get Random values from mySQL -

i have table columns subjects,questions,exam,question id, table want random values display.

for every every question have used:

$singlesql = mysql_query("select * questions id='$question' order rand() limit 1"); 

for every subject:

$singlesql = mysql_query("select * questions id='$question' , subject='ayooooo' order rand() limit 1"); 

i want display random questions when ever page loads , hen next question asked.

quiz.php?question=' 

how should use here?

javascript:

function getquestion() {     var hr = new xmlhttprequest();     hr.onreadystatechange = function () {         if (hr.readystate == 4 && hr.status == 200) {             var response = hr.responsetext.split("|");             if (response[0] == "finished") {                 document.getelementbyid('status').innerhtml = response[1];             }             var nums = hr.responsetext.split(",");             document.getelementbyid('question').innerhtml = nums[0];             document.getelementbyid('answers').innerhtml = nums[1];             document.getelementbyid('answers').innerhtml += nums[2];         }     }     hr.open("get", "questions.php?question=" + <? php echo $question; ?> , true);     hr.send(); }  function x() {     var rads = document.getelementsbyname("rads");     (var = 0; < rads.length; i++) {         if (rads[i].checked) {             var val = rads[i].value;             return val;         }     } }  function post_answer() {     var p = new xmlhttprequest();     var id = document.getelementbyid('qid').value;     var url = "useranswers.php";     var vars = "qid=" + id + "&radio=" + x();     p.open("post", url, true);     p.setrequestheader("content-type", "application/x-www-form-  urlencoded");     p.onreadystatechange = function () {         if (p.readystate == 4 && p.status == 200) {             document.getelementbyid("status").innerhtml = '';             var url = 'quiz.php?question=<?php echo $next; ?>';             window.location = url;         }     }      p.send(vars);     document.getelementbyid("status")