Destructuring in PHP

What is destructuring (list, [])?

If you don’t know what destructuring is yet, it’s easier to start with an example:

$coords = [-48.876667, -123.393333];
list($latitude, $longitude) = $coords;

echo $latitude, ', ', $longitude;

// Output:
// -48.876667, -123.393333

Impressive? Then let’s move on!

Based on the official PHP documentation, destructuring is a language construct used to assign values to a list of variables in a single operation.

By the way, starting from PHP version 7.1, you can use [] instead of list. Therefore, the example above will change as follows:

$coords = [-48.876667, -123.393333];
[$latitude, $longitude] = $coords;

Even more beautiful!

What other features destructuring provide?

Element skip

For example, if the array contains more values than you need, you can simply skip it:

$point = [3, 14, 15];
[$x,, $z] = $point;

echo $x, ', ', $z;

// Output:
// 3, 15

Associative arrays

You can also “unpack” an associative array, but in this case, you need to specify its keys:

$user = [
    'first_name' => 'John',
    'last_name' => 'Doe',
    'age' => 71,
    'job' => 'HR',
];

['first_name' => $firstName, 'last_name' => $lastName, 'job' => $job] = $user;

echo $firstName, ' ', $lastName, ' - ', $job;

// Output:
// John Doe - HR

When destructuring associative arrays, the order can be disregarded and elements can be skipped.

Variables swap

Sometimes in programming, there are moments when it is necessary to use the variable $tmp, some of these cases can be solved using destructuring:

$a = 1;
$b = 2;

[$b, $a] = [$a, $b];

echo $a, ' ', $b;

// Output:
// 2 1

Destructuring in the foreach loop

It’s very convenient to unpack an array in a foreach loop, as the inner part of the loop can look cleaner and simpler.

$users = [
    [
        'first_name' => 'John',
        'last_name' => 'Doe',
    ],
    [
        'first_name' => 'Jane',
        'last_name' => 'Doe',
    ],
];

foreach ($users as ['first_name' => $firstName, 'last_name' => $lastName]) {
    echo $firstName, ' ', $lastName . "\n";
}

// Output:
// John Doe
// Jane Doe

When can you use destructuring in real life?

With functions that return arrays

The ideal candidates are parse_url, pathinfo, and other less popular functions.

['host' => $host] = parse_url("https://haprycon.dev/destructuring-in-php/");

echo $host;

// Output
// haprycon.dev

['extension' => $extension] = pathinfo('/var/www/html/images/picture.png');

echo $extension;

// Output:
// png

['month' => $month] = getdate();

echo $month;

// Output:
// November

Explode

$email = "contact@haprycon.dev";
[$username, $domain] = explode('@', $email);

echo $username, ' ', $domain;

Variables swap

For example, in the popular Bubble Sort algorithm, you can get rid of the variable $tmp:

$a = [2, 5, 12, 6, 2, 5, 7, 2, 4, 8];

for ($i = count($a) - 1; $i > 0; $i--) {
    $swap = false;

    for ($j = 0; $j < $i; $j++) {
      if ($a[$j] > $a[$j + 1]) {
//      With $tmp varialbe
//      $tmp = $a[$j];
//      $a[$j] = $a[$j+1];
//      $a[$j+1] = $tmp;

//      With destructuring and without $tmp variable
        [$a[$j], $a[$j + 1]] = [$a[$j + 1], $a[$j]];
        
        $swap = true;
      }
    }
    
    if (!$swap) {
    	break;
    }
  }

Return statements that return multiple values

function getResponse(): array
{
    return ['error', 'Error message'];
}

[$status, $message] = getResponse();

echo 'Status: ', $status, ', Message: ', $message;

// Output
// Status: error, Message: Error message

What are the pitfalls?

Everything would be fine if it weren’t for the problems. For example, when destructuring an associative array without specifying keys, you will receive E_NOTICE or E_WARNING starting from PHP 8.

$user = ['first_name' => 'John', 'last_name' => 'Doe'];
[$firstName, $lastName] = $user;

// PHP < 8
// Notice: Undefined offset: 0 
// Notice: Undefined offset: 1

// PHP >= 8
// Warning: Undefined array key 0
// Warning: Undefined array key 1

You will face the same issue if the index does not exist in the array.

$user = ['first_name' => 'John', 'last_name' => 'Doe'];
['age' => $age] = $user;

// PHP < 8
// Notice: Undefined index: age

// PHP >= 8
// Warning: Undefined array key "age"

$user = ['John', 'Doe'];
[$firstName, $lastName, $age] = $user;

// PHP < 8
// Notice: Undefined offset: 2

// PHP >= 8
// Warning: Undefined array key 2

We hope this article was helpful to you. Make your code better with destructuring. Good luck!

What is destructuring (list, [])?

What other features destructuring provide?

Element skip

Associative arrays

Variables swap

Destructuring in the foreach loop

When can you use destructuring in real life?

With functions that return arrays

Explode

Variables swap

Return statements that return multiple values

What are the pitfalls?

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