questions on sort array by time in php
array_multisort
sorts more than one array at once. However, it works on an array of columns, so the foreach
loop is needed to get a column of the times. After building up this list, you can then perform the multisort. The $points
array is ordered according to the indices in $times
, as per this example in the docs.
However, you don't need to perform the sort inside the foreach
, as that means the sort happens 4 times (in your example). It only needs to happen once:
foreach ($points as $key => $val) {
$time[$key] = $val[0];
}
array_multisort($time, SORT_ASC, $points);
The function uasort()
takes a comparison callback function. You can use this to compare two timestamps.
$arr = array(
array('2011-10-02 05:30:00','20'),
array('2011-10-04 09:30:00','12'),
array('2011-10-01 13:30:00','25'),
array('2011-10-03 02:30:00','31')
);
function timecomp($a,$b)
{
// Subtracting the UNIX timestamps from each other.
// Returns a negative number if $b is a date before $a,
// otherwise positive.
return strtotime($b[0])-strtotime($a[0]);
}
uasort($arr,'timecomp');
print_r($arr);
The above code will return
(
[1] => Array
(
[0] => 2011-10-04 09:30:00
[1] => 12
)
[3] => Array
(
[0] => 2011-10-03 02:30:00
[1] => 31
)
[0] => Array
(
[0] => 2011-10-02 05:30:00
[1] => 20
)
[2] => Array
(
[0] => 2011-10-01 13:30:00
[1] => 25
)
)