how to count number of days in between two dates in php?

 count number of days in between two dates in php

<?php
$date1 = date_create("2017-04-15");$date2 = date_create("2017-05-18");
//difference between two dates$diff = date_diff($date1,$date2);
//count daysecho 'Days Count - '.$diff->format("%a");?>