Understanding PHP’s array_fill() Function: Syntax, Parameters, Return Values, and Examples

PHP is a popular language for web development; its array_fill() function fills an array with a specified value.

1. Function Overview

The array_fill() function creates a new array by filling it with the same value, requiring three arguments: start_index, num, and value.

2. Parameters

start_index

: the starting index (non‑negative integer). num: the number of elements to fill (non‑negative integer). value: the value to assign to each element (any type).

3. Return Value

The function returns the newly created array; if start_index or num is negative it returns false, and if num is zero it returns an empty array.

4. Examples

Simple one‑dimensional array:

<?php
$array1 = array_fill(0, 5, 10);
print_r($array1);
?>

Output:

Array ( [0] => 10 [1] => 10 [2] => 10 [3] => 10 [4] => 10 )

Two‑dimensional array example:

<?php
$array2 = array_fill(0, 3, array_fill(0, 3, 1));
print_r($array2);
?>

Output:

Array ( [0] => Array ( [0] => 1 [1] => 1 [2] => 1 ) 
          [1] => Array ( [0] => 1 [1] => 1 [2] => 1 ) 
          [2] => Array ( [0] => 1 [1] => 1 [2] => 1 ) )

5. Summary

The array_fill() function enables quick creation of arrays with uniform values, but careful attention to its parameters and return values is required for correct usage.