What are the differences between using date_diff() and strtotime() for calculating date intervals in PHP, and when should each be used?

When calculating date intervals in PHP, date_diff() is used to calculate the difference between two dates and returns a DateInterval object, while strtotime() is used to convert a date string into a Unix timestamp. date_diff() is more suitable for calculating intervals between two dates, while strtotime() is useful for manipulating dates and time calculations. 

// Using date_diff() to calculate date intervals
$date1 = new DateTime('2022-01-01');
$date2 = new DateTime('2022-01-10');
$interval = $date1->diff($date2);
echo $interval->format('%R%a days');

// Using strtotime() to manipulate dates
$date = strtotime('2022-01-01');
$new_date = strtotime('+10 days', $date);
echo date('Y-m-d', $new_date);

Keywords

date_diff strtotime date intervals PHP calculation

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