phpは月の最小日を決定します

$ar = array(  '2014-01-01',  '2014-01-02',  '2014-01-22',  '2014-02-22',  '2014-02-26',  '2014-03-03',  '2014-03-25',  '2014-03-28',);$r1 = $r2 = array();foreach($ar as $d) {  list($y, $m, $d) = explode('-', $d);  if(! isset($r1[$y.$m])) $r1[$y.$m] = 32;  $r1[$y.$m] = min($r1[$y.$m], $d);  if(! isset($r2[$y.$m])) $r2[$y.$m] = 0;  $r2[$y.$m]++;}print_r($r1);print_r($r2);

$arr = array('2014-01-01','2014-01-02','2014-01-22','2014-02-22','2014-02-26','2014-03-03','2014-03-25','2014-03-28');sort($arr);$out = array();foreach ($arr as $key => $value) {	$mouth = date('n',strtotime($value));	if(!in_array($mouth, array_keys($out))) $out[$mouth] = $value;}var_dump($out);

$arr = array('2014-01-01','2014-01-02','2014-01-22','2014-02-22','2014-02-26','2014-03-03','2014-03-25','2014-03-28');$newArr = array_map('cout', $arr);function cout($n){	return date('n',strtotime($n));}print_r ( array_count_values ( $newArr ));