Date math and string conversion

[Claus Mygind]

I am passing my app a string "20140920" (last day of the week)

I want to create two date strings to use on a MySQL query where I retrieve all records for the week.

The two variables should be the first and last day of the week like this.

$end = "20140920"
$start = "20140914"

I have tried a number of combinations of code to get this but I'm just stuck. A simple example would be appreciated.

[Claus Mygind]

Some times it's the little things that get you. Was passing " around the string.

//setup date range
/*
---------------------------------
end of pay period
already a string in format needed
no action required
---------------------------------
*/
$lastDay = $_REQUEST['WeekEnding'];
 
 
/*
----------------------------------------------
start of pay period
make a date object with "new DateTime($var)"
----------------------------------------------
*/
$x = new DateTime($_REQUEST['WeekEnding']);
 
/*
--------------------------------------
do math operation on date object 
using $var->sub() to subtract or 
$var->add to add days to date object
--------------------------------------
*/
$x->sub(new DateInterval('P6D'));
 
/*
------------------------------------
convert date object 
back into a string with format()
------------------------------------
*/
$firstDay = $x->format('Ymd');