How to order an array based on dates? - php

Question

I have the following array
$dates = array(
'2015-02-13',
'2015-04-21',
'2015-08-18',
'2015-11-26',
'2015-09-15',
'2015-01-07',
'2015-02-11',
'2015-07-14',
'2015-03-02',
);
I would like to sort this array from longest ago to most recent date.
foreach ($dates as $date) {
$date = new DateTime($date);
// The logic I need
}
Could you help me out?
Edit
I would like to note that the date format can vary. To elaborate, I have dates in my database formatted as YYYY-MM-DD, YYYY/MM/DD, DD-MM-YYYY and DD/MM/YYYY.
But as suggested below I can reformat the date and build a new array. So this will probably not be an issue.

Answer 1

The dates you have are in shortened ISO8601 format, i.e. YYYY-MM-DD.
These have the nice feature that the lexical sort order is the same as date order. So, just sort the array using the default sort function. It'll work.
When handling date strings inside code it's always a good idea to have ISO8601 be the canonical internal date format. Convert user-supplied to that as soon as possible, and if the user requires output to be in their own locale then defer that to as late as possible. Of course, using a "proper" date object is better still!

Answer 2

Just try to convert all date formats to time numbers.
<?php
$finalArray = array();
foreach ($datesInFormatA as $date) {
$finalArray[] = strtotime($date);
}
foreach ($datesInFormatB as $date) {
$finalArray[] = strtotime($date);
}
And for all of your date formats do this. Then you will have an array of numbers that you can sort them easily.
$finalArray = sort($finalArray);

Answer 3

You can convert with strtotime() to safely date-manipulating and then you can reorder the array:
$dates = array(
'2015-02-13',
'2015-04-21',
'2015-08-18',
'2015-11-26',
'2015-09-15',
'2015-01-07',
'2015-02-11',
'2015-07-14',
'2015-03-02',
);
$newArray = array();
foreach($dates as $value) {
$newArray[] = strtotime($value);
}
sort($newArray);
var_dump($newArray);

Answer 4

Use PHP sort function
<?php
$dates = array(
'2015-02-13',
'2015-04-21',
'2015-08-18',
'2015-11-26',
'2015-09-15',
'2015-01-07',
'2015-02-11',
'2015-07-14',
'2015-03-02',
);
sort($dates);
var_dump($dates);
Output:
array(9) {
[0]=>
string(10) "2015-01-07"
[1]=>
string(10) "2015-02-11"
[2]=>
string(10) "2015-02-13"
[3]=>
string(10) "2015-03-02"
[4]=>
string(10) "2015-04-21"
[5]=>
string(10) "2015-07-14"
[6]=>
string(10) "2015-08-18"
[7]=>
string(10) "2015-09-15"
[8]=>
string(10) "2015-11-26"
}
Remember, this works for 'Y-m-d' format. For other formats you need to convert to date format using strtotime() function and need to proceed. Something like this (standard formats):
function sortFunction( $a, $b ) {
return strtotime($a[0]) - strtotime($b[0]);
}
usort($dates, "sortFunction");
Dates in the m/d/y or d-m-y formats are disambiguated by looking at
the separator between the various components: if the separator is a
slash (/), then the American m/d/y is assumed; whereas if the
separator is a dash (-) or a dot (.), then the European d-m-y format
is assumed.

Answer 5

Try this quick sort algorithm.
What it does is, it compares the date as Unix Timestamp which starts from Jan 01 1970 (UTC)) and sort it and put into the array.
Converting to Unix Timestamp asures the ISO8601 date format.
$dates = array(
'2015-02-13',
'2015-04-21',
'2015-08-18',
'2015-11-26',
'2015-09-15',
'2015-01-07',
'2015-02-11',
'2015-07-14',
'2015-03-02',
);
function quick_sort($array)
{
// find array size
$length = count($array);
// base case test, if array of length 0 then just return array to caller
if($length <= 1){
return $array;
}
else{
// select an item to act as our pivot point, since list is unsorted first position is easiest
$pivot = $array[0];
// declare our two arrays to act as partitions
$left = $right = array();
// loop and compare each item in the array to the pivot value, place item in appropriate partition
for($i = 1; $i < count($array); $i++)
{
if(strtotime($array[$i]) < strtotime($pivot)){
$left[] = $array[$i];
}
else{
$right[] = $array[$i];
}
}
// use recursion to now sort the left and right lists
return array_merge(quick_sort($left), array($pivot), quick_sort($right));
}
}
$sorted = quick_sort($dates);
print_r($sorted);
// Output
Array
(
[0] 2015-01-07
[1] 2015-02-11
[2] 2015-02-13
[3] 2015-03-02
[4] 2015-04-21
[5] 2015-07-14
[6] 2015-08-18
[7] 2015-09-15
[8] 2015-11-26
)

Answer 6

I have one solution for you, hope this will help you to sort as this is working for me.
I recommend you to use usort() With a custom function:
$dates = array(
'2015-02-13',
'2015-04-21',
'2015-08-18',
'2015-11-26',
'2015-09-15',
'2015-01-07',
'2015-02-11',
'2015-07-14',
'2015-03-02',
);
function date_fun_compare($a, $b)
{
$t1 = strtotime($a['datetime']);
$t2 = strtotime($b['datetime']);
return $t1 - $t2;
}
usort($dates, 'date_fun_compare');
Hope this will help you.

Answer 7

php does not work well in format MM DD YYYY because of the confusion between day and month.
For your first and second condition YYYY-MM-DD or YYYY/MM/DD you can follow this solution:
$dates = array(
'2015-02-13',
'2015-04-21',
'2015-08-18',
'2015-11-26',
'2015-09-15',
'2015-01-07',
'2015-02-11',
'2015-07-14',
'2015-03-02',
);
function date_sorter($a, $b)
{
$t1 = strtotime($a);
$t2 = strtotime($b);
return $t1 - $t2;
}
usort($dates, 'date_sorter');
// check the output
echo '<pre>'.print_r($dates,1).'</pre>'
OUTPUT:
Array
(
[0] => 2015-01-07
[1] => 2015-02-11
[2] => 2015-02-13
[3] => 2015-03-02
[4] => 2015-04-21
[5] => 2015-07-14
[6] => 2015-08-18
[7] => 2015-09-15
[8] => 2015-11-26
)
FYI: you can try changing - to /
If the format is like YYYY DD MM (whatever it is / or -) you can see the following solution:
Sample input:
$dates = array(
'13/02/2015',
'21/04/2015',
'18/08/2015',
'26/11/2015',
'15/09/2015',
'07/01/2015',
'11/02/2015',
'14/07/2015',
'02/03/2015',
);
Function:
function date_sorter($a, $b )
{
$da = DateTime::createFromFormat('d/m/Y', $a); // define date format d/m/Y
$db = DateTime::createFromFormat('d/m/Y', $b); // define date format d/m/Y
$t1 = strtotime($da->format('Y-m-d'));
$t2 = strtotime($db->format('Y-m-d'));
return $t1 - $t2;
}
usort($dates, 'date_sorter');
echo '<pre>'.print_r($dates,1).'</pre>';
Output:
Array
(
[0] => 07/01/2015
[1] => 11/02/2015
[2] => 13/02/2015
[3] => 02/03/2015
[4] => 21/04/2015
[5] => 14/07/2015
[6] => 18/08/2015
[7] => 15/09/2015
[8] => 26/11/2015
)
However, perhaps it will help you.

Answer 8

Well, since you mentioned that you have all your dates in the following formats: YYYY-MM-DD, YYYY/MM/DD, DD-MM-YYYY and DD/MM/YYYY
First you will need to convert them to a single format, lets use YYYY-MM-DD.
Then as already mentioned, you will just need to regular sort it.
Included how you could re format your strings, without having to create a date object per each just for sorting.
$dates = array(
'2015-02-13',
'2015-04-21',
'2015-08-18',
'2015-11-26',
'2015-09-15',
'2015/01/07',
'2015-02-11',
'2015/07/14',
'2015-03-02',
'08/01/2015',
'08-04-2015',
);
array_walk($dates, function(&$el){
if($el[4] !== '-' && $el[4] !== '/'){
// Ugly, I know, but is the fastest
$el = $el[6] . $el[7] .$el[8] . $el[9] . '-' . $el[3] . $el[4] . '-' . $el[0] . $el[1];
// Or just explode, revert array and implode
}elseif($el[4] !== '-'){
$el = str_replace('/', '-', $el);
}
});
sort($dates);
print_r($dates);
Will print:
Array
(
[0] => 2015-01-07
[1] => 2015-01-08
[2] => 2015-02-11
[3] => 2015-02-13
[4] => 2015-03-02
[5] => 2015-04-08
[6] => 2015-04-21
[7] => 2015-07-14
[8] => 2015-08-18
[9] => 2015-09-15
[10] => 2015-11-26
)
Want it to other way, just use rsort($dates) instead.

Answer 9

Depending on the format of your date (in your case is ok with Y-m-d) just perform a sort
sort($dates);