Square Brackets

Square brackets are used with the array syntax: they delimit the offset in the index.

Square brackets are also used to define array: this is the short syntax array, where [1,2,3] is equivalent to array(1,2,3).

Square brackets are also used to embody the list() command: this is the short syntax array, where [$a, $b, $c] is equivalent to list($a,$b,$c). The list() and array() syntaxes are distinguished between one another as list() must be in a writing context, such as the left side of an assignation or the values of a foreach, while the array() must be in a reading context, such as the right side of an assignation, or parameter passing.

Finally, an empty square bracket is the append operator.

<?php

//Definition of arrays
$array = [1, 2, 3];

// Accessing element in the array
print $array[2]; // 3

// equivalent to list
[$a, $b] = $array;

$array[] = 4;
// $array == [1, 2, 3, 4];

?>

Related : Array, Index For Arrays, List, Array Append, Curly Brackets, Parenthesis