<!-- HTML -->
<ul>
	<li data-id="1">This is a question</li>
	<li data-id="2">Another question</li>
</ul>
<!-- /HTML -->

<!-- Javascript -->
setTimeout(function(){
	$.ajax({
		url: 'poll.php',
		type: 'GET',
		dataType: 'json',
		success: function(response){
			// Response will be a JSON object returned from the PHP script
			check_changed_questions(response);
		}
	});
});

function check_changed_questions(questions){
	for(i=0; i<questions.length; i++){
		var id = questions[i].id;
		var html_question = $('li[data-id=' + id + ']').html();
		var db_question = questions[i].questions;

		if(db_question != html_question){
			// Means the question in the database does not
			// match the one on the page

		}
	}
}

<!-- /Javascript -->

<!-- PHP (poll.php) -->
<?php
$sql = "SELECT * FROM questions";
$data = array();
$result = mysql_query($sql);

while($row = mysql_fetch_assoc($result))
{
	$data[] = array('id' => $row['id'], 'question' => $row['question']);
}

echo json_encode($data);
?>