next_week_by_day_name.php

<?php
function dateNext($dayName)
{
    $timeVar = time();

    while($dayName != date("D", $timeVar) && $timeVar - time() <= 604800) // Run this loop untill we find the next day with the given weekname, or untill we've looked more than a week ahead (something went wrong)
    {
        $timeVar += 86400 // Add a day
    }

    if($timeVar - time() > 604800) // If we looped past what would be a week, return -1
    {
        return -1;
    }

    $seconds_since_morning = (int)date("s", $timeVar) + (int)date("i", $timeVar); * 60 +  (int)date("G", $timeVar) * 60 * 60; // Use the date function to get the time in hours minutes and seconds, and convert to seconds

    return $timeVar - $seconds_since_morning; // Return the Unix timestamp for 00:00:00 on the next occurance of the date
}
?>