list() / Short Array Destructuring

Also Known As

TL;DR

Explanation

PHP's list() construct (and its [] shorthand since PHP 7.1) destructures arrays into named variables. PHP 7.1 enabled key-based destructuring (['name' => $name, 'age' => $age] = $row) for associative arrays, greatly improving database row handling. Nested destructuring is supported. list() is especially useful with foreach for unpacking tuple-like arrays: foreach ($rows as [$id, $name]) and for swapping variables: [$a, $b] = [$b, $a]. Accessing a non-existent key emits a notice — validate structure first.

Common Misconception

Why It Matters

Common Mistakes

• Using list() with associative arrays without specifying keys — positional destructuring of associative arrays is error-prone.
• Not checking that the source array has enough elements — undefined index notices on short arrays.
• Confusing list() (assignment) with array() (creation) — similar syntax, completely different purpose.
• Using list() in PHP < 7.1 for associative array destructuring — key-based list() was added in 7.1.

Code Examples

// Positional list() on associative array — order-dependent and fragile:
[$name, $email] = $user; // Relies on array key order — breaks if order changes

// Safe:
['name' => $name, 'email' => $email] = $user; // Explicit key mapping

// list() / [] — destructure arrays into variables
[$first, $second, $third] = [10, 20, 30];

// Skip elements
[, $second] = getCoordinates(); // ignore x, capture y

// Nested
[[$x1, $y1], [$x2, $y2]] = [[1,2],[3,4]];

// Associative (PHP 7.1+)
['name' => $name, 'age' => $age] = $user;

// In foreach — unpack each row
$points = [[1,2,'A'], [3,4,'B']];
foreach ($points as [$x, $y, $label]) {
    echo "$label: ($x, $y)\n";
}

// Classic swap without temp variable
[$a, $b] = [$b, $a];

References

• ↗ https://www.php.net/manual/en/language.types.array.php#language.types.array.destructuring

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