array_fill(): Filling an array with values

$status = array_fill(0, 4, 'pending');
print_r($status);

$new_array = array_fill ($start_key, $number, $value);

Example 1

$result=array_fill(2,4,'plus2net');
foreach ($result as $key => $val) {
echo "$key -> $val <br>";
}

2 -> plus2net 
3 -> plus2net 
4 -> plus2net 
5 -> plus2net

Example 2 with negative $start_key

$result=array_fill(-3,4,'plus2net');
foreach ($result as $key=>$val) { // PHP 8
echo "$key -> $val <br>";
}

-3 -> plus2net 
-2 -> plus2net 
-1 -> plus2net 
0 -> plus2net 

Example 3: Filling an Array with Default Values for Form Processing

When processing forms with multiple inputs, array_fill() can help initialize empty fields with default values. This is useful to avoid undefined index errors.

$input_fields = array_fill(0, 5, '');
print_r($input_fields);

This will create an array of 5 elements, each initialized to an empty string, which can be assigned to form inputs.

Example 4: Filling an Associative Array

While array_fill() creates indexed arrays, we can simulate an associative array by using custom keys:

$keys = ['name', 'email', 'age'];
$filled_array = array_combine($keys, array_fill(0, count($keys), 'default'));
print_r($filled_array);

This example fills an array with predefined keys, assigning 'default' to each key.

Example 5: Filling an Array Conditionally Based on Values

In some cases, you may want to fill an array only under certain conditions. This example demonstrates filling an array if a value meets a condition:

$numbers = range(1, 10);
$filled_array = array_map(function($num) {
    return $num % 2 == 0 ? 'even' : $num;
}, $numbers);
print_r($filled_array);

This creates an array of numbers but replaces even numbers with the string 'even'.

Example 6: Filling a Multi-dimensional Array

You can also use array_fill() to create multi-dimensional arrays by nesting the function:

$matrix = array_fill(0, 3, array_fill(0, 3, 0));
print_r($matrix);

This creates a 3x3 matrix (two-dimensional array) filled with zeros.

Use Case: Preallocating Arrays for Memory Efficiency

In performance-critical applications, preallocating arrays can help optimize memory usage, especially when you know the array's size in advance:

$preallocated_array = array_fill(0, 1000000, null);

This creates a large array of 1,000,000 elements, each initialized to *null*, which can be filled later.

Example 7: Combining array_fill() with array_merge() for Flexible Initialization

We can combine array_fill() with other array functions for more flexibility:

$default_values = array_fill(0, 5, 'N/A');
$additional_values = ['age' => 25, 'name' => 'John'];
$final_array = array_merge($additional_values, $default_values);
print_r($final_array);

This merges predefined values with default ones, ensuring that the array has all required keys.

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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