How to Sort an Array of Objects by a Specific Property in PHP?

Sorting Objects in an Array by Property

When dealing with arrays of objects, you might encounter the need to organize them based on a specific field or property. This article addresses the question of how to sort an array of objects by a specified field, such as name or count.

To accomplish this, PHP provides us with the usort function. It takes an array as its first argument and a callable as its second argument, which serves as a comparison function. This comparison function should return an integer indicating the result of the comparison: -1 if the first object should come before the second, 0 if they're equal, and 1 if the second object should come before the first.

Let's consider an example with an array of objects:

$array = [
    (object) ['name' => 'Mary Jane', 'count' => 420],
    (object) ['name' => 'Johnny', 'count' => 234],
    (object) ['name' => 'Kathy', 'count' => 4354],
];

To sort this array by the name field, we can define a comparison function as follows:

function cmp($a, $b) {
    return strcmp($a->name, $b->name);
}

Now we can use usort to sort the array:

usort($array, 'cmp');

This will sort the array in ascending order of the name field.

Alternative Approaches

In addition to the traditional comparison function, PHP offers various alternative approaches for sorting:

• Anonymous functions: These allow you to define the comparison function inline, e.g.:

usort($array, function($a, $b) {
    return strcmp($a->name, $b->name);
});

• Inside a class: If you have a class, you can define a comparison method and pass it to usort, e.g.:

class MyComparator {
    public function cmp($a, $b) {
        return strcmp($a->name, $b->name);
    }
}

$array = usort($array, [new MyComparator(), 'cmp']);

• Arrow functions (PHP 7.4 ): These provide a concise way to define comparison functions, e.g.:

usort($array, fn($a, $b) => strcmp($a->name, $b->name));

Comparing Numeric Fields

When comparing numeric fields, such as the count field in our example, you can use the following comparison function:

fn($a, $b) => $a->count - $b->count

Alternatively, PHP 7 introduced the Spaceship operator (<=>) which can be used for such comparisons, e.g.:

fn($a, $b) => $a->count <=> $b->count

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