Question

I currently use this to to open new content in a div (so I don’t have to refresh the whole page):

file1.php

<?php
//db connection

if ($res = $mysqli->query("SELECT field FROM table")) {

    /* determine number of rows result set */
    $row = $res->num_rows;

    echo "$row";

    $res->close();
}
?>

jquery.js

$.ajax({ 
  url: "file1.php", 
//this will run as soon as the php script echos the answer 
  success: function(result){  
$('#div1').html(result); 
} 
});

page1.php

<div id="div1">
</div>

Code Updated

Answer 1

From your comments i understand you are a bit confused, so i’ll do my best to explain:

1. $.load is ajax wrapped in a more convenient method, so you are already using ajax without knowing it.
2. From what i understand, you get the result variable from DB, it is not just a static number in some page, so what you need is to make an ajax call to the script that fetches this result from DB and return it to the callback function:

somePage.php:

$result = ...//get data from DB
echo $result; 

jquery:

$('#someBtn').click(function(){
$.ajax({
      url: "somePage.php",
    //this will run as soon as the php script echos the answer
      success: function(result){ 
    $('#content').html(result);
    }
    });
});

Of course you’ll need a button in your HTML:

<input type="button" id="someBtn"/>

this is roughly how you do it. I suggest you take a look at jquery.ajax(), it is not that hard.