Calculate current quarter and previous quarter(s)

A simple PHP function to calculate current quarter and previous quarters.

/**
 * gets quarter start/end date either for current date or previous according to $i
 * i.e. $i=0 => current quarter, $i=1 => 1st full quarter, $i=n => n full quarter
 * @param  $i
 * @return array();
 */
function get_quarter($i=0) {
	$y = date('Y');
	$m = date('m');
	if($i > 0) {
		for($x = 0; $x < $i; $x++) {
			if($m <= 3) { $y--; }
			$diff = $m % 3;
			$m = ($diff > 0) ? $m - $diff:$m-3;
			if($m == 0) { $m = 12; }
		}
	}
	switch($m) {
		case $m >= 1 && $m <= 3:
			$start = $y.'-01-01 00:00:01';
			$end = $y.'-03-31 00:00:00';
			break;
		case $m >= 4 && $m <= 6:
			$start = $y.'-04-01 00:00:01';
			$end = $y.'-06-30 00:00:00';
			break;
		case $m >= 7 && $m <= 9:
			$start = $y.'-07-01 00:00:01';
			$end = $y.'-09-30 00:00:00';
			break;
		case $m >= 10 && $m <= 12:
			$start = $y.'-10-01 00:00:01';
			$end = $y.'-12-31 00:00:00';
	    		break;
	}
	return array(
		'start' => $start,
		'end' => $end,
		'start_nix' => strtotime($start),
		'end_nix' => strtotime($end)							
	);
}