PHP two-dimensional array sorting method (array_multisort usort)

For example, an array like the following:

$users = array(
    array('name' => 'tom', 'age' => 20)
    , array('name' => 'anny', 'age' => 18)
    , array('name' => 'jack', 'age' => 22)
);

I hope it can be sorted by age from small to large. The author has sorted out two methods and shared them with you.

1. Use array_multisort

Using this method will be more troublesome. You need to extract the age and store it in a one-dimensional array, and then arrange it in ascending order by age. The specific code is as follows:

$ages = array();
foreach ($users as $user) {
    $ages[] = $user['age'];
}
array_multisort($ages, SORT_ASC, $users);

After execution, $users is a sorted array, which can be printed out to see. If you need to sort by age in ascending order first, and then by name in ascending order, the method is the same as above, that is, extract an additional name array. The final sorting method is called like this:

array_multisort($ages, SORT_ASC, $names, SORT_ASC, $users);

2. Use usort

The biggest advantage of using this method is that you can customize it Define some more complex sorting methods. For example, sort in descending order by name length:

usort($users, function($a, $b) {
            $al = strlen($a['name']);
            $bl = strlen($b['name']);
            if ($al == $bl)
                return 0;
            return ($al > $bl) ? -1 : 1;
        });

Anonymous functions are used here, and they can be extracted separately if necessary. Among them, $a and $b can be understood as elements under the $users array. You can directly index the name value, calculate the length, and then compare the lengths.

The author prefers the second method because it eliminates the step of extracting the sorted content into a one-dimensional array, and the sorting method is more flexible.

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