How to add leading zeros to numbers in PHP

Posted on Oct 04, 2022

Learn how you can add leading zeros to numbers in PHP


Sometimes, you need to add pad a number with leading zeros like numbers displayed in electrical devices.

To add leading zeros to numbers in PHP, you need to format your number as a string using the sprintf() function.

Hereโ€™s an example of creating a 4 digit number with sprintf():

<?php
// ๐Ÿ‘‡ 4 digit pad numbers
print sprintf("%04d", 333); // 0333
print PHP_EOL;
print sprintf("%04d", 1234); // 1234
print PHP_EOL;
print sprintf("%04d", 12); // 0012
?>

In the sprintf() function above, the format of the string is defined as โ€œformat the integer with 4 digits (4d) and pad it with leading zeros (0)โ€.

To change the format, you only need to adjust the number before the d letter.

The example below shows how to create 6 and 8 digit numbers:

<?php

// ๐Ÿ‘‡ 6 digit pad numbers
print sprintf("%06d", 1234); // 001234
print PHP_EOL;

// ๐Ÿ‘‡ 8 digit pad numbers
print sprintf("%08d", 1234); // 00001234
?>

Because numbers in PHP canโ€™t have leading zeros naturally, you need to format the numbers using the sprintf() function.

You can also format negative numbers with leading zeros:

<?php
// ๐Ÿ‘‡ 6 digit pad numbers
print sprintf("%06d", -123); // -00123
print PHP_EOL;
print sprintf("%06d", -654); // -00654
?>

Alternatively, you can also use the str_pad() function to pad numbers with leading zeros.

But this function canโ€™t be used to pad negative numbers as shown below:

<?php
// ๐Ÿ‘‡ 6 digit pad numbers
print str_pad(1234, 6, 0, STR_PAD_LEFT); // 001234
print PHP_EOL;

// ๐Ÿ‘‡ 8 digit pad numbers
print str_pad(1234, 8, 0, STR_PAD_LEFT); // 00001234
print PHP_EOL;

// ๐Ÿ‘‡ negative number has wrong format
print str_pad(-1234, 6, 0, STR_PAD_LEFT); // 0-1234
?>

Padding negative numbers with the str_pad() function will produce an invalid format.

But if you never need to format negative numbers with leading zeros, then itโ€™s fine to use the str_pad() function.

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