PHP str_pad() Function: Syntax, Parameters, Return Value, and Usage Examples

The str_pad() function in PHP pads a string to a specified length by adding characters to the left, right, or both sides.

Function Syntax

<code>str_pad(string $input, int $pad_length, string $pad_string [, int $pad_type = STR_PAD_RIGHT]): string</code>

Parameters

$input : the string to be padded.

$pad_length : the desired length after padding.

$pad_string : the character(s) used for padding.

$pad_type : optional, one of STR_PAD_LEFT , STR_PAD_RIGHT , or STR_PAD_BOTH ; default is STR_PAD_RIGHT .

Return Value

Returns the padded string.

Basic Example

<code>$input = "Hello";
$pad_length = 10;
$pad_string = "-";
$pad_type = STR_PAD_LEFT;
$result = str_pad($input, $pad_length, $pad_string, $pad_type);
echo $result; // -----Hello</code>

Advanced Uses

1. String Alignment

<code>$text = "Hello";
$length = 10;
$pad_string = " ";
$leftAligned = str_pad($text, $length, $pad_string, STR_PAD_RIGHT);
$rightAligned = str_pad($text, $length, $pad_string, STR_PAD_LEFT);
$centerAligned = str_pad($text, $length, $pad_string, STR_PAD_BOTH);

echo $leftAligned . "\n";
echo $rightAligned . "\n";
echo $centerAligned . "\n"; // Outputs: "Hello      \n      Hello\n   Hello   "
</code>

2. String Truncation

<code>$text = "Hello World";
$length = 10;
$pad_string = " ";
$paddedText = str_pad($text, $length, $pad_string);
$truncatedText = substr($paddedText, 0, $length);
echo $truncatedText; // Hello Worl
</code>

3. Numeric Formatting

<code>$number = "123";
$length = 6;
$pad_string = "0";
$formattedNumber = str_pad($number, $length, $pad_string, STR_PAD_LEFT);
echo $formattedNumber; // 000123
</code>

Summary

The str_pad() function is a versatile tool for controlling string length and formatting in PHP, supporting basic padding, alignment, truncation, and numeric zero‑padding, thereby enhancing string manipulation flexibility for backend development.