How to Custom Sort Multidimensional Arrays Based on a Specific Key in PHP?

Custom Sorting of Multidimensional Arrays

Sorting multidimensional arrays can be a common task in programming. This article demonstrates how to sort such an array based on a specific key using the PHP usort() function.

Understanding the Task

Consider the following multidimensional array where each element represents a record:

<code class="php">Array (
    [0] => Array
        (
            [iid] => 1
            [invitee] => 174
            [nid] => 324343
            [showtime] => 2010-05-09 15:15:00
            [location] => 13
            [status] => 1
            [created] => 2010-05-09 15:05:00
            [updated] => 2010-05-09 16:24:00
        )

    [1] => Array
        (
            [iid] => 1
            [invitee] => 220
            [nid] => 21232
            [showtime] => 2010-05-09 15:15:00
            [location] => 12
            [status] => 0
            [created] => 2010-05-10 18:11:00
            [updated] => 2010-05-10 18:11:00
        ))</code>

Sorting by a Key

To sort this array by the "status" key, we need to define a comparison function that determines the order of the elements.

<code class="php">function cmp($a, $b) {
    if ($a['status'] == $b['status']) {
        return 0;
    }
    return ($a['status'] < $b['status']) ? -1 : 1;
}</code>

This function compares the "status" values of two elements. If the values are equal, it returns 0. If the first element has a lower "status" value than the second, it returns -1. Otherwise, it returns 1.

Using usort()

We can now use the usort() function to sort the array using our comparison function:

<code class="php">usort($array, "cmp");</code>

This will sort the array in ascending order based on the "status" key. The modified array will have its elements rearranged accordingly.

Customizing the Comparison

The comparison function can be customized to sort the array based on any key. Simply modify the function to compare the desired key values. This provides flexibility in sorting multidimensional arrays based on different criteria.

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