Sort multidimensional array (PHP) - date complications and counting - php

Question

I have the following output of an array using PHP. I need to do two things... First, I need to sort the array so it prints by the most recent date. I can't use a simple sort, because the date is outputted in the format mm/dd/yyyy (and not a regular time stamp) ...
Then I need to count how many rows exist for each year.
So, in the example below, I would need to know that there are ...
2 entries from 2010
2 entries from 2011
1 entry from 2012
Stop counting when there are no more rows
Since the year is not separate from the rest of the date digits, this also complicates things...
Array
(
[0] => Array
(
[racer_date] => 11/15/2010
[racer_race] => Test Row 4
[racer_event] => 321
[racer_time] => 16
[racer_place] => 12
[racer_medal] => 1
)
[1] => Array
(
[racer_date] => 7/15/2010
[racer_race] => Test Row 3
[racer_event] => 123
[racer_time] => 14
[racer_place] => 6
[racer_medal] => 0
)
[2] => Array
(
[racer_date] => 7/28/2011
[racer_race] => Test Row
[racer_event] => 123
[racer_time] => 10
[racer_place] => 2
[racer_medal] => 2
)
[3] => Array
(
[racer_date] => 10/9/2011
[racer_race] => Test Row 2
[racer_event] => 321
[racer_time] => 12
[racer_place] => 3
[racer_medal] => 3
)
[4] => Array
(
[racer_date] => 10/3/2012
[racer_race] => World Indoor Championships (final)
[racer_event] => 400m
[racer_time] => 50.79
[racer_place] => 1
[racer_medal] => 1
)
)

Answer 1

function cmp($a, $b)
{
if (strtotime($a["racer_date"]) == strtotime($b["racer_date"])) {
return 0;
}
return (strtotime($a["racer_date"]) < strtotime($b["racer_date"])) ? -1 : 1;
}
usort($array, "cmp");
call your array $array, and above code will sort it..
And to count entities you'll need to run foreach and check date('Y',strtotime($a["racer_date"])) in that foreach which will give you year in 4 digit..