The date_diff() is an inbuilt function in PHP which is used to calculate the difference between two dates.

1. Code:

<?php 
	function getDifferenceBetweenTwoDates($mySqlDate1, $mySqlDate2){
		$date1 = date_create($mySqlDate1);
		$date2 = date_create($mySqlDate2);
		$diff = date_diff($date1, $date2);
		return (int)$diff->format('%R%a');
	}
	$mySqlDate1 = "2018-11-15 00:00:00";
	$mySqlDate2 = "2018-11-5 00:00:00";
	echo(getDifferenceBetweenTwoDates($mySqlDate1, $mySqlDate2));
    ?> 

2. Example:

Input:

"2018-11-15 00:00:00"
"2018-11-5 00:00:00"

Output:

-10