Sort function works wrong with filemtime PHP

Question

I'm trying to sort files by modification date using PHP.

I'm using filemtime function then sort function using the following code:

<?php

$array2 = array();
$images = glob("*.*");
foreach($images as $image) {
echo "Last modified: ".date("F d Y H:i:s.",filemtime($image));
echo "<br>";

array_push($array2,date("F d Y H:i:s.",filemtime($image)));
}
//echo array2;
sort($array2);
echo "<br>";

foreach ($array2 as $ar)
{
    echo $ar;
    echo "<br>";

}
//$array2[$image] = date("F d Y H:i:s.",filemtime($image));

?>

and the output is like this

Last modified: June 21 2013 15:48:42.
Last modified: June 12 2013 14:43:10.
Last modified: April 09 2013 15:39:13.
Last modified: June 12 2013 14:00:14.
Last modified: June 21 2013 16:08:58.
Last modified: July 15 2013 12:44:28.
Last modified: July 15 2013 12:48:48.
Last modified: July 15 2013 14:42:19.
Last modified: July 15 2013 14:54:48.
Last modified: April 09 2013 15:39:13.
Last modified: June 21 2013 15:34:30.
Last modified: June 21 2013 15:56:32.

April 09 2013 15:39:13.
April 09 2013 15:39:13.
July 15 2013 12:44:28.
July 15 2013 12:48:48.
July 15 2013 14:42:19.
July 15 2013 14:54:48.
June 12 2013 14:00:14.
June 12 2013 14:43:10.
June 21 2013 15:34:30.
June 21 2013 15:48:42.
June 21 2013 15:56:32.
June 21 2013 16:08:58.

here you can see July is between April and June

can anyone please guide me to the problem ?

Answer 1

The problem is that you are sorting the human-readable representations of the dates, so obviously April comes first (it starts with A).

What you need to do is something like

foreach($images as $image) {
    array_push($array2, filemtime($image));
}

sort($array2);

// and now, AFTER sorting get the formatted dates 
foreach ($array2 as $ts)
{
    echo date("F d Y H:i:s.", $ts);
}

Some tips:

1. You can get the last modified times for your files in just one line with

   $array2 = array_map('filemtime', $images);
   

2. date depends on the system timezone. Make sure you have set it properly with date_default_timezone_set before doing anything.