unexpected results with sort(array) - php

Question

Odd.....
// array sort test
$_ar = array(
0 => "2015-02-23",
1 => "2015-02-21",
2 => "2015-02-28",
3 => "2015-03-20",
4 => "2015-03-14",
5 => "2015-03-21",
6 => "2015-02-21",
7 => "2015-02-28",
8 => "2015-03-07",
9 => "2015-03-14",
);
$_ar = sort($_ar);
var_dump($_ar);
// returns bool(true)
$__ar = array(
0 => "2015 02 23",
1 => "2015 02 21",
2 => "2015 02 28",
3 => "2015 03 20",
4 => "2015 03 14",
5 => "2015 03 21",
6 => "2015 02 21",
7 => "2015 02 28",
8 => "2015 03 07",
9 => "2015 03 14",
);
$__ar = sort($__ar);
var_dump($__ar);
// returns bool(true)
$ar = array(
0 => "20150223",
1 => "20150221",
2 => "20150228",
3 => "20150320",
4 => "20150314",
5 => "20150321",
6 => "20150221",
7 => "20150228",
8 => "20150307",
9 => "20150314",
);
$ar = sort($ar);
var_dump($ar);
// returns bool(true)
I am expecting this to return the array sorted by the date value. I thought maybe it was the - (hyphen) or spaces, but in all my examples my PHP var_dump simply returns bool(true) for each instance. Can someone confirm they get the same, or point out what I must be missing....
I have tried asort() - still the same.

Answer 1

You don't have to assign the return value of sort(). For more information about sort() see the manual: http://php.net/manual/en/function.sort.php
And a quote from there:
Returns TRUE on success or FALSE on failure.
So just to this:
sort($_ar);
Side Note:
I wouldn't recommend you to define variables with underscores at the start of the name, since this already get's used by defined php variables e.g. super globals or magic constants

Answer 2

The sort and asort function returns bool value. Just call this function and it will sort the array, don't store it , it returns true or false.Use the code below
// array sort test
$_ar = array(
0 => "2015-02-23",
1 => "2015-02-21",
2 => "2015-02-28",
3 => "2015-03-20",
4 => "2015-03-14",
5 => "2015-03-21",
6 => "2015-02-21",
7 => "2015-02-28",
8 => "2015-03-07",
9 => "2015-03-14",
);
sort($_ar);
var_dump($_ar);
// returns bool(true)
$__ar = array(
0 => "2015 02 23",
1 => "2015 02 21",
2 => "2015 02 28",
3 => "2015 03 20",
4 => "2015 03 14",
5 => "2015 03 21",
6 => "2015 02 21",
7 => "2015 02 28",
8 => "2015 03 07",
9 => "2015 03 14",
);
$__ar = sort($__ar);
var_dump($__ar);
// returns bool(true)
$ar = array(
0 => "20150223",
1 => "20150221",
2 => "20150228",
3 => "20150320",
4 => "20150314",
5 => "20150321",
6 => "20150221",
7 => "20150228",
8 => "20150307",
9 => "20150314",
);
sort($ar);
var_dump($ar);
// returns bool(true)
Hope this helps you