How to Implement array_pad in PHP Without Using Built-In Functions

In PHP, the array_pad function allows you to increase the length of an array by adding values to the start or end. But what if you want to create this functionality without using built-in functions? This article will walk you through creating a custom implementation of array_pad from scratch.

What Is array_pad and Why Use a Custom Function?

The array_pad function is used to extend an array to a specified length by filling it with a given value. Creating a custom version helps you understand the logic behind array manipulation and provides flexibility for unique use cases.

Step 1: Understand the Parameters of array_pad

The custom array_pad function will take three parameters:

1. Array: The original array to be extended.
2. Size: The desired length of the array.
3. Value: The value to be used for padding.

Step 2: Create the Custom Function

Here is how you can implement a custom array_pad function:

function customArrayPad($array, $size, $value) {
    $currentLength = count($array);
    
    // Determine if padding is needed
    if (abs($size) <= $currentLength) {
        return $array; // No padding needed
    }
    
    // Calculate the number of elements to add
    $padLength = abs($size) - $currentLength;
    $paddedArray = $array; // Start with the original array
    
    if ($size > 0) {
        // Add elements to the end
        for ($i = 0; $i < $padLength; $i++) {
            $paddedArray[] = $value;
        }
    } else {
        // Add elements to the beginning
        for ($i = 0; $i < $padLength; $i++) {
            array_unshift($paddedArray, $value);
        }
    }
    
    return $paddedArray;
}

Step 3: Test the Custom Function

Here’s how to use this function:

// Example 1: Pad array to a length of 5 with value 0
$originalArray = [1, 2, 3];
$result = customArrayPad($originalArray, 5, 0);
print_r($result);

// Example 2: Pad array to a length of -6 with value 'X'
$originalArray = ['A', 'B', 'C'];
$result = customArrayPad($originalArray, -6, 'X');
print_r($result);

Output:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 0
    [4] => 0
)
Array
(
    [0] => X
    [1] => X
    [2] => X
    [3] => A
    [4] => B
    [5] => C
)

Building a custom array_pad function in PHP is a great way to strengthen your understanding of loops, conditionals, and array manipulation. While PHP’s built-in functions are efficient, coding your own solutions equips you with problem-solving skills and greater control.

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