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

Use The biggest advantage of this method is that you can customize some more complex sorting methods. For example, sort in descending order according to the length of the name:

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

Anonymous function is used here, and it 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 there is no step to extract the sorted content into a one-dimensional array, and the sorting method is more flexible.

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