在PHP中循环特定日期（交叉月份）

I'm working on a project that produces reports on a weekly basis, so if today's date is "2013/09/05" the code has to figure out what was the date seven days ago, which is "2013/08/29", taking into account that some months are longer than others.

and then i want to run the dates against the database looking for matches ...

this is what i have done so far but its not working.

  // Start date
        $text = explode('/', $date); //2013/09/05
        $day = $text[2];
        $month = $text[1];
        $year = $text[0];
        $past_day = $day - 7; //-2


  // determine if $past_day is negative 
if ($past_day < 0){

    $month = $month - 1; //08
    $var = $day - 0; //2
    $num = cal_days_in_month(CAL_GREGORIAN, $month, $year);
    $var = ($num - $var); // 29
    $start_date = $year."/".$month."/".$var;

}else{
    $start_date = $year."/".$month."/".$past_day;
}

Thanks alot guys!

try this :)

$date = "2013/09/05";
// Start date
    $text = explode('/', $date); //2013/09/05
    $day = $text[2];
    $month = $text[1];
    $year = $text[0];
    $past_day = $day - 7; //-2


// determine if $past_day is negative 
if ($past_day < 0){

$month = $month - 1; //08

$var = ($past_day)*-1; //2
$num = cal_days_in_month(CAL_GREGORIAN, $month, $year);
$var = ($num - $var); // 29
$start_date = $year."/".$month."/".$var;

}else{
$start_date = $year."/".$month."/".$past_day;
}