How to Use PHP's str_pad Function for String Padding

When writing PHP code, you often need to manipulate strings, and sometimes you need to pad a string to a specific length. The built‑in str_pad function can accomplish this by adding a specified string to the left or right side of the original string until the desired length is reached.

Basic Syntax:

string str_pad ( string $input , int $pad_length [, string $pad_string = " " [, int $pad_type = STR_PAD_RIGHT ]] )

The parameters are: $input: the string to be padded. $pad_length: the length of the resulting string after padding. $pad_string: the string used for padding (default is a space). $pad_type: specifies the direction of padding (right, left, or both).

Usage Examples

Below are several examples demonstrating how to use the str_pad function:

1. Pad a string on the right side:

$input = "Hello";
$pad_length = 10;
$pad_string = "World";
$pad_type = STR_PAD_RIGHT;
$result = str_pad($input, $pad_length, $pad_string, $pad_type);

// Output: "HelloWorld"

In this example, the original string "Hello" (length 5) is padded on the right with "World" until the total length reaches 10.

2. Pad a string on the left side:

$input = "Hello";
$pad_length = 10;
$pad_string = "World";
$pad_type = STR_PAD_LEFT;
$result = str_pad($input, $pad_length, $pad_string, $pad_type);

// Output: "WorldHello"

Here, the string "Hello" is padded on the left with "World" to reach the length of 10.

3. Pad a string on both sides:

$input = "Hello";
$pad_length = 9;
$pad_string = "World";
$pad_type = STR_PAD_BOTH;
$result = str_pad($input, $pad_length, $pad_string, $pad_type);

// Output: "WorldHelloWorld"

In this case, the string "Hello" is padded evenly on both sides with "World" until the total length becomes 9.

The str_pad function is useful for various string‑processing scenarios, allowing flexible control over padding length and content by adjusting the pad_length and pad_string parameters.