Sort multidimensial array by date - php

Question

I've tried this with usort, but I didn't succeed.
I've the following array:
array(
[0] => array(
'date' => '3:6:2012'
),
[1] => array(
'date' => '5:5:2012'
),
[2] => array(
'date' => '20:12:2011'
)
)
The date is in d:m:yyyy format, so no leading zero's.
I want to sort the array to get this:
array(
[0] => array(
'date' => '20:12:2011'
),
[1] => array(
'date' => '5:5:2012'
),
[2] => array(
'date' => '3:6:2012'
)
)
I've tried it this way:
function cmp($a, $b) {
if($a['date'] = $b['date']) {
return 0;
}
$partsa = explode(":", $a['date']);
$partsb = explode(":", $b['date']);
$daya = $partsa[0];
$montha = $partsa[1];
$yeara = $partsa[2];
$dayb = $partsb[0];
$monthb = $partsb[1];
$yearb = $partsb[2];
if($yeara < $yearb) {
return -1;
} elseif($yeara > $yearb) {
return 1;
} elseif($yeara == $yearb) {
if($montha < $monthb) {
return -1;
} elseif($montha > $monthb) {
return 1;
} elseif($montha == $monthb) {
if($daya < $dayb) {
return -1;
} elseif($daya > $dayb) {
return 1;
} elseif($daya == $dayb) {
return 0;
}
}
}
}
but this doesn't give good results with usort...
How to do this?

Answer 1

You can create a temporary array with normalized dates (yyyymmdd), then use array_multisort:
$arr = array(
array(
'date' => '3:6:2012'
),
array(
'date' => '5:5:2012'
),
array(
'date' => '20:12:2011'
),
array(
'foo' => 'no date here'
),
);
foreach($arr as $key=>$row) {
if(isset($row['date'])) {
$date = explode(':',$row['date']);
$date = $date[2] . str_pad($date[1],2,'0',STR_PAD_LEFT) . str_pad($date[0],2,'0',STR_PAD_LEFT);
$sort_arr[$key] = $date;
} else {
$sort_arr[$key] = null;
}
}
array_multisort($sort_arr, SORT_ASC, $arr);
print_r($arr);

Answer 2

PHP offers the function strcmp, that's doing the comparing stuff for us. In order to compare the dates correctly, we create timestamp out of it.
But at first we need to parse the string: exploding by : and finally throwing them to mktime.
function cmp($a, $b) {
$a = explode(':', $a['date']);
$a = mktime(0, 0, 0, intval($a[1]), intval($a[0]), intval($a[2]));
$b = explode(':', $b['date']);
$b = mktime(0, 0, 0, intval($b[1]), intval($b[0]), intval($b[2]));
return strcmp($a, $b);
}
Note: The first three arguments of mktime are hours, minutes and seconds and can be ignored in this scenario.

Answer 3

First, make them dates (normal, php-readable dates):
foreach($array as $innerarray){
foreach($innerarray as $key=>$value){
$date = explode(":", $value);
$date = date($date[2]."/".$date[1]."/".$date[0]);
$array[$innerarray][$key] = $date;
}
}
After this, you can sort them with the following function:
function sort_bydate($a, $b) {
return strnatcmp($a['date'], $b['date']);
}
// sort by date
usort($data, 'sort_bydate');
This should do the trick.
By the way, I would advise to not use arrays in arrays, because it is useless in your case.