How to Format a Number with Leading Zeros in PHP

When working with data in PHP, you might encounter scenarios where you need to format numbers with leading zeros.

This is a common requirement for various applications, such as displaying dates, times, or unique identifiers in a consistent format.

PHP provides a simple way to achieve this using the str_pad function. In this article, we'll explore how to format a number with leading zeros in PHP.

Using the "str_pad" Function to Add Zeros

The str_pad function is a versatile tool in PHP for adding padding to a string, and it's particularly useful for formatting numbers with leading zeros.

Here's how you can use it:

$number = 42;
$width = 5; // Total width of the formatted number

$formattedNumber = str_pad($number, $width, '0', STR_PAD_LEFT);

echo $formattedNumber; // Output: "00042"

In this example:

  1. We have a variable $number with a value of 42.

  2. The $width variable specifies the total width of the formatted number. In this case, we want a width of 5, which means the number will be padded with leading zeros to reach that width.

  3. We use the str_pad function with four parameters:

    • The first parameter is the input number, $number.
    • The second parameter is the desired width, $width.
    • The third parameter is the character to use for padding, which is '0' (zero) in this case.
    • The fourth parameter, STR_PAD_LEFT, indicates that the padding should be added to the left (before the number).
  4. The result, stored in $formattedNumber, is "00042" with leading zeros.

By adjusting the values of $number and $width, you can easily format numbers with the desired number of leading zeros to fit your specific requirements.

Practical Use Cases

Formatting numbers with leading zeros is essential in various applications:


Formatting a number with leading zeros in PHP is a straightforward task, thanks to the str_pad function.

Whether you're working with dates, times, unique identifiers, or any other numerical data that requires a specific format, this method allows you to achieve consistency and readability in your output.

By customizing the width and the character used for padding, you can tailor the formatting to your application's requirements.