Question

I just can’t get my head around it. What do I need to write in my php file to return something to the $.post function?

<script type="text/javascript">
    function SubmitToDatabase(uName, uComment)
    {
        $.post("write_something_to_mysql_b.php", {name: uName, comment: uComment});
        return false;
    }
</script> 

This works, but there is no return value from the PHP file

Answer 1

// php:
$output['result']    = 'hello!!!';
echo json_encode($output); // json encode here
exit;

// jquery:
$.post(
"write_something_to_mysql_b.php",
{
    name : uName,
    comment : uComment
},
function(output) { // callback function to catch your php output
    // console.debug(output['result']);
    alert(output['result']);
    // output hello!!!
},
'json'); // json requirement here

json is just one of the possibilities to require data from backend side. Others are: xml, json, script, text, html. For each one of these formats you must to return data from backend in a suitable way. For example for text just echo 'hello!!!; exit;