Master PHP’s str_pad(): Padding, Alignment, Truncation & Formatting Explained

str_pad()

is a PHP function for padding strings, allowing characters to be added to the left, right, or both sides to reach a specified length.

Basic syntax of str_pad()

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

Parameter description:

$input

: the string to be padded. $pad_length: the length of the resulting string. $pad_string: the padding characters. $pad_type: padding type, can be STR_PAD_LEFT (left), STR_PAD_RIGHT (right), or STR_PAD_BOTH (both); default is STR_PAD_RIGHT.

Return value:

Returns the padded string.

Example:

Below is a simple example demonstrating how to use str_pad() to add padding characters to the left side of a string:

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

Output:

-----Hello

Usage of str_pad()

Beyond basic padding, str_pad() can be combined with other string functions for more complex tasks.

1. String alignment

str_pad()

can be used for left, right, and center alignment. Example:

$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 . "
";
echo $rightAligned . "
";
echo $centerAligned . "
";

Output:

Hello     
    Hello
  Hello

2. String truncation

str_pad()

can be used together with substr() to truncate strings. Example:

$text = "Hello World";
$length = 10;
$pad_string = " ";
$paddedText = str_pad($text, $length, $pad_string);
$truncatedText = substr($paddedText, 0, $length);
echo $truncatedText;

Output:

Hello Worl

3. Formatting strings

str_pad()

can format numeric strings by adding leading zeros. Example:

$number = "123";
$length = 6;
$pad_string = "0";
$formattedNumber = str_pad($number, $length, $pad_string, STR_PAD_LEFT);
echo $formattedNumber;

Output:

000123

Summary

This article detailed the basic usage, parameters, and examples of PHP’s str_pad() function. It demonstrated how the function can be used for padding, alignment, truncation, and formatting, enhancing string handling flexibility and efficiency in PHP development.