I need help to be able to credit tenants that are in my system after every 30 days of stay. Code in either PHP, AJAX, jQuery

You need to set a timestamp of when to start and a then a cron job to check when 30 days have be reached.. When the cron job runs, it will update code to set the database update credit. You would most likly do this in php if you are posting in php section of this forum.

Thanks Guyz... Atleast am some where with the following code:

<?php

include '../connection.php';

    $today = new DateTime('2014-7-14 20:10:10');
    $appt  = new DateTime('2014-8-15 20:10:10');
    $days_until_appt = $appt->diff($today)->days;


if ($days_until_appt>=30)
{

    $sql = "SELECT username FROM users WHERE position = 'Tenant'";
    $result = mysql_query($sql) or die(mysql_error());

    echo '<table align="center" border="1" cellpadding="0">';
    echo '<tr align="center"><th> Payee'.'</th><th> Credit'.'</tr>';

    while($row = mysql_fetch_array($result))
    {
    echo '<tr><th>'.$row['username'].'</th>'.'<br/>';
    $rw = $row['username'];

    $sq = "SELECT * FROM finance WHERE payee = '$rw'";
    $res = mysql_query($sq) or die(mysql_error());
    $rw = mysql_fetch_array($res);

    $total = $rw['credit']+ 3000;
    echo '<th>'.$rw['credit'].'</th></tr>'.'<br/>';
    }
    echo'</table>';
}
?>