<?php
//2015年の日付を１つ１つ取得し、計算する
$begin = new DateTime('2015-01-01');
$end = new DateTime('2015-12-31');

$interval = new DateInterval('P1D'); //P：整数　D：day　一日おき
$daterange = new DatePeriod($begin, $interval ,$end);

$count = 0;
foreach($daterange as $date){
    $m = $date->format("m");
    $d = $date->format("d");
    $d_array = str_split($d);
    if($m == $d_array[0] + $d_array[1]){
        $count++;
    }
}
echo (string)$count . "\n";