Fix binary operation +, - or * on string

By type casting to integer.

Author: steef

DateFormatter/DateFormat/DayOfYearTransformer.php

@@ -25,7 +25,7 @@ class DayOfYearTransformer extends Transformer
      */
     public function format(\DateTime $dateTime, $length)
     {
-        $dayOfYear = $dateTime->format('z') + 1;
+        $dayOfYear = (int) $dateTime->format('z') + 1;
 
         return $this->padLeft($dayOfYear, $length);
     }

DateFormatter/DateFormat/FullTransformer.php

@@ -315,7 +315,7 @@ protected function calculateUnixTimestamp(\DateTime $dateTime, array $options)
         preg_match_all($this->regExp, $this->pattern, $matches);
         if (\in_array('yy', $matches[0])) {
             $dateTime->setTimestamp(time());
-            $year = $year > $dateTime->format('y') + 20 ? 1900 + $year : 2000 + $year;
+            $year = $year > (int) $dateTime->format('y') + 20 ? 1900 + $year : 2000 + $year;
         }
 
         $dateTime->setDate($year, $month, $day);