PHP array_fill Function: Fill Array with Same Value

You can use the array_fill function in PHP when you must fill an array with one value. You may want to set default values in a form or to prepare a list with repeated values for quick use.

Understand the array_fill Function in PHP

The array_fill function creates an array and fills it with one value. You set the start index, the number of elements, and the value.

Here is the syntax:

array_fill($start_index, $count, $value)

• $start_index – The index for the first element in the array.
• $count – The number of elements in the array.
• $value – The value that will fill each element.

PHP makes a loop inside its code when you run the function. The loop starts at the given index and runs until it creates the required number of elements. Each element gets the same value.

You can use this function to prepare arrays with default options. It can also help in tests where you need repeated data. You may also use it when you must fill large arrays quickly.

Here is a quick example:

$array = array_fill(0, 4, 'apple');
print_r($array);

This code creates an array with four items. Each item holds the word “apple”. The index starts from zero and ends at three.

Here is the output:

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

Use the array_fill with Arrays

Create indexed arrays with array_fill:

$list = array_fill(0, 5, 10);
print_r($list);

This will produce indexes from zero to four with the value ten. The output:

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

Use array_fill with numeric indexes:

$data = array_fill(5, 3, 'yes');
print_r($data );

This creates keys five to seven with the value “yes”. The output:

Array
(
    [5] => yes
    [6] => yes
    [7] => yes
)

Combine array_fill with array_map for Dynamic Values:

$base = array_fill(0, 5, 0);
$result = array_map(function($v, $i) { return $i * 2; }, $base, array_keys($base));
print_r($result);

This creates values that depend on the index. The output:

Array
(
    [0] => 0
    [1] => 2
    [2] => 4
    [3] => 6
    [4] => 8
)

So, how does array_fill handle negative indexes?

If you use a negative start index, PHP still creates the array. The index begins at the negative number and grows from there.

For example:

$array = array_fill(-2, 3, 'test');

This creates keys -2, -1, and 0. Here is the output:

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

Examples of array_fill in PHP

Fill a List with the Same Number:

$numbers = array_fill(0, 5, 100);
print_r($numbers);

This creates five items with the number one hundred. The count begins at index zero. You can use it to prepare lists with fixed values before you add more data.

Start from a Non-zero Index:

$data = array_fill(3, 4, 'ready');
print_r($data);

This fills keys three to six with the word “ready”. It can help when you must keep lower indexes for other data.

Use Negative Index:

$items = array_fill(-3, 3, 'on');
print_r($items);

This starts from index -3 and ends at -1. It is useful when you need to match certain key rules in a program.

Wrapping Up

In this article, you learned the array_fill function and its uses in PHP. You also saw how it works with different types of indexes and how it pairs with other functions.

Here is a quick recap:

• array_fill creates arrays with repeated values.
• You can set the start index to zero, a positive number, or a negative number.
• It works with other functions to produce dynamic results.
• It works the same in PHP 7 and 8, but error handling differs

FAQs

$result = array_fill(0, 5, "apple");  
print_r($result);

$arr1 = array_fill(0, 3, "x");  
print_r($arr1);

$arr2 = array_fill_keys(["a", "b", "c"], "x");  
print_r($arr2);

$arr = array_fill(-2, 3, "pear");  
print_r($arr);

$defaults = array_fill(0, 4, "N/A");  
print_r($defaults);

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