How to sort by key or value in PHP array

How to sort by key or value in PHP array

While developing PHP applications, we often need to sort arrays. PHP provides many sorting functions that can sort arrays based on their keys or values. In this article, we'll show you how to sort by key or value in a PHP array and show you how to do it with a code example.

1. Sort by key

It is relatively simple to sort by the key of the array. We can use PHP’s built-in function ksort() to implement key sorting. The ksort() function sorts the array in ascending order according to the keys. If we need to sort in descending order, we can use the krsort() function.

The following is a sample code for sorting by key:

$fruits = array("apple" => 3, "orange" => 2, "banana" => 1);
ksort($fruits);

foreach ($fruits as $key => $value) {
    echo $key . ": " . $value . "<br>";
}

The output will be:

apple: 3
banana: 1
orange: 2

2. Sort by value

To sort by the value of the array, we can use PHP's built-in function asort() to achieve this. The asort() function sorts the array in ascending order. If we need to sort in descending order, we can use the arsort() function.

The following is a sample code to sort by value:

$fruits = array("apple" => 3, "orange" => 2, "banana" => 1);
asort($fruits);

foreach ($fruits as $key => $value) {
    echo $key . ": " . $value . "<br>";
}

The output result will be:

banana: 1
orange: 2
apple: 3

3. Custom sorting rule

In addition to using the built-in sorting function, we can also use custom sorting rules to sort the array. In PHP, we can use the usort() function to implement custom sorting.

The following is a sample code that uses custom sorting rules to sort an array:

$fruits = array("apple" => 3, "orange" => 2, "banana" => 1);
usort($fruits, function($a, $b) {
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
});

foreach ($fruits as $key => $value) {
    echo $key . ": " . $value . "<br>";
}

The output result will be:

banana: 1
orange: 2
apple: 3

In the above code, we use Anonymous function to define custom collation. Anonymous functions determine the sort order by comparing array values.

To sum up, by using PHP’s built-in sorting function along with custom sorting rules, we can easily sort the array by key or value. The flexibility of these sorting functions allows us to handle array sorting needs more efficiently when developing PHP applications.

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