Sort an array of dates in PHP

We are given an array of multiple dates in (Y-m-d) format. We have to write a program in PHP to sort all the dates in the array in decreasing order. Examples :

Input : array("2018-06-04", "2014-06-08", "2018-06-05")
Output : 2018-06-05 2018-06-04 2014-06-08

Input : array("2016-09-12", "2009-09-08", "2009-09-09")
Output : 2016-09-12 2009-09-09 2009-09-08

Here we have some common methods:

PHP usort() function

by defining a comparator function. The comparator function will accept two date arguments which will be converted to integer timestamp using strtotime() function and then compared to sort date based on integer timestamp value.

Inbuilt Functions used

• strtotime() : This function changes a given date string into timestamp (large int value).
• usort() : This function sorts the given array as per a user defined comparison function.

Below is the PHP implementation of above idea:

Output :

Array
(
 [0] => 2016-09-12
 [1] => 2009-09-09
 [2] => 2009-09-06
)

Using array_multisort() with Custom Date Conversion

Sort an array of dates in PHP by converting them to a sortable format using array_map(), then utilize array_multisort() on the converted dates to achieve chronological order

Example:

Array
(
 [0] => 2022-11-20
 [1] => 2023-01-05
 [2] => 2023-05-15
 [3] => 2024-03-10
)