PHP Date Array Sorting

Sorting a date array in PHP can be tricky, especially if the dates are not in a standardized format.

In your specific case, you have an array of dates in different formats, such as "11-01-2012" and "01-01-2014". Using the asort function, which sorts arrays by values in ascending order, will not work in this case because it treats each date as a string and ignores the year-month-day hierarchy.

To correctly sort your array, you can use a custom sorting function that converts each date into a sortable format before comparison.

Converting Dates to UNIX Timestamps

One simple method is to convert each date into a UNIX timestamp using the strtotime() function. UNIX timestamps represent dates as the number of seconds since 1970-01-01, which makes them easy to compare and sort.

Here's an example of using a custom sorting function to sort the dates using UNIX timestamps:

usort($arr, function ($a, $b) {
    return strtotime($a) - strtotime($b);
});

This function will take two dates as input (represented by the $a and $b variables) and return the difference between their UNIX timestamps. The resulting array will be sorted in ascending chronological order.

Additional Considerations

It's important to note that this method assumes that all dates are in the same format. If your dates come from different sources or use different date formats, you will need to use a more robust date parsing and conversion library.