PHP MySQL Update to 0 at End of foreach()

Question

I'm trying to update multiple cells in a MySQL database based on a previous update date. I am having an issue with unchanged, trailing cells updating to 0.

Database table looks like this (default = 0 for Day#; N = last update date):

id--Run--Day1--Day2--Day3--Day4

1----N------1-----2-----3----4

The code below does the following:

1. Retrieves the database entry under column= Run, id=1
2. Subtracts that date from today's date.
3. Uses that difference to move database for Day1->Day4 to the left.

Example database table when the difference is 2 days:

id--Run--Day1--Day2--Day3--Day4

1----N------3-----4-----3----4

My issue is that I need it to change all trailing Days to 0. So in this example, Day3 & Day4 should both be 0. I've been trying out another foreach() statement within but can't get the logic behind it. Would someone please point me in the right direction?

$DaysColumnRange2 = range (1, 4);
foreach ($DaysColumnRange2 as $DaysColumnRangeLoop2){
    $SubtractedDaysColumns2 = $DaysColumnRangeLoop2 - $diff2format;
    $MoveToNewDay2 = ${$Day.$SubtractedDaysColumns2};
    $OriginalOldDay = $diff2format + $SubtractedDaysColumns2;
    $sql2 = "UPDATE users SET Day$MoveToNewDay2='$OriginalOldDay' WHERE id='$id'";
    if ($conn->query($sql2) === TRUE) {
        echo "RECORDS UPDATED SUCCESFULLY";
    } else {
        echo "Error updating record: " . $conn->error;
            }
}

I'll update this first post with my attempts as I continue to work on it.

(this is not a great way of doing it, but this is what I was able to put together since Cron jobs wasn't reliable & I haven't yet figured out how MySQL Triggers work)

**

------------------UPDATE--------------

**

This section is to clarify my question.

Let's say this is my database right now:

id--Run--Day1--Day2--Day3--Day4

1----N------1-----2-----3----4

I run the code below where $diff2format = 2:

//>Database credentials + login here

//Retrieve database entry for Run
$id = 1;
$todaysdateupdate = date("Y-m-d");
$lastupdatequeryresult = mysql_query("SELECT Run FROM users WHERE id='$id'");
$lastupdaterow = mysql_fetch_assoc($lastupdatequeryresult);

//Compare Run date to today's date.
$date3=date_create($lastupdaterow['Run']);
$date4 = date_create(date("Y-m-d"));
$diff2=date_diff($date3,$date4);
$diff2format = $diff2->format("%a");

//Day1, 2, 3, etc...
$result1 = mysql_query("SELECT Day1 FROM users WHERE id='$id'");
$row1 = mysql_fetch_assoc($result1);


//Hard coded "Day#" variables
$Day = "Day";
$Day1 = $row1['Day1'];
$Day2 = $row2['Day2'];
$Day3 = $row3['Day3'];
$Day4 = $row4['Day4']; //etc

//MY QUESTION STARTS HERE****************
$DaysColumnRange2 = range (1, 4);
foreach ($DaysColumnRange2 as $DaysColumnRangeLoop2){
    $SubtractedDaysColumns2 = $DaysColumnRangeLoop2 - $diff2format;
    $MoveToNewDay2 = ${$Day.$SubtractedDaysColumns2};
    $OriginalOldDay = $diff2format + $SubtractedDaysColumns2;
    $sql2 = "UPDATE users SET Day$MoveToNewDay2='$OriginalOldDay' WHERE id='$id'";
    if ($conn->query($sql2) === TRUE) {
        echo "RECORDS UPDATED SUCCESFULLY";
    } else {
        echo "Error updating record: " . $conn->error;
            }
}

The output for the database is below. Basically it copied Day3 moved it 2 times to the left, then copied Day4 and also moved 2 times to the left. Nothing changed with Day3 or Day4.

id--Run--Day1--Day2--Day3--Day4

1----N------3-----4-----3----4

But I need it to output this instead:

id--Run--Day1--Day2--Day3--Day4

1----N------3-----4-----0----0