PHP在while循环中将日期（'Y-m-d'，strtotime（x天'））减少（x-1）

I'm trying to decrease a counter variable (x) within this date function:

date('Y-m-d', strtotime(x days'))

in a while loop like this:

$Today = date('Y-m-d', strtotime('-1 days'));

output thus far: 2015-06-25

$x = -1;

while ($row = mysql_fetch_array($result1)) {

$Today = date('Y-m-d', strtotime('$x days'));

... 

$x = $x - 1;
}

desired output on next iteration of while loop: 2015-06-24 and so on ...

What you have already will work, except that it has to be done with a double quoted string to interpolate the variable, as in strtotime("$x days") – @Michael Berkowski