PHP array_fill() Function: Usage, Parameters, Return Values, and Examples

PHP is a widely used language for web development, and its functions enhance code readability, maintainability, and reusability. One useful function is array_fill(), which fills an array with a single value.

1. Function Overview

The array_fill() function creates a new array by filling each element with the same value. It requires three parameters: start index, number of elements, and the value to fill.

2. Parameters

The three parameters are: start_index: the starting index, must be a non‑negative integer. num: the number of elements to fill, must be a non‑negative integer. value: the value to assign to each element; it can be of any type.

3. Return Value

The function returns a new array containing the filled elements. If start_index or num is negative, it returns false. If num is zero, it returns an empty array.

4. Examples

Simple one‑dimensional example:

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

Output:

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

Two‑dimensional 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 ) )

The second example demonstrates nesting array_fill() to create a 3×3 matrix filled with the value 1.

5. Summary

The array_fill() function helps programmers quickly create an array and populate it with a uniform value, making it a valuable tool in PHP development. Proper understanding of its parameters and return values is essential for effective use.