How to properly format a number with leading zeros in PHP

  1. Using a string to substitute the number
  2. substr() to add leading zeros in PHP
  3. printf() / sprintf() to add leading zeros in PHP
  4. str_pad() to add leading zeros in PHP

In PHP, numbers or integers with leading zeros can have different values with unexpected results.

Example:

$number = 0987654321; //this is an octal number
$number = 0x987654321 // this is a hexadecimal number
$number = 0b0987654321 // this is a binary number

To make sure that the number will not lose its “natural” meaning, there are several ways to try like using a string instead of a number or by using different functions such as substr, printf() / sprintf() and str_pad.

Using a string to substitute the number

The easiest approach; just simply to use string as a substitute for the number.

$number = "0987654321";

When To Use:

  1. There’s no required length of the output.
  2. There’s no exception to the number that it always need a leading zero.

substr() to add leading zeros in PHP

This method clips the numbers from the left when the string length exceeded.

If the start is negative, the returned string will start from the start'th character from the end of the string.

Example:

$number = 98765;
$length = 10;
$string = substr(str_repeat(0, $length).$number, - $length);

//output: 0000098765

When To Use:

  1. When there’s a fixed length of the output string.
  2. Adding zeros when the string is less than the length.

printf() / sprintf() to add leading zeros in PHP

To pad an output for a fixed length, when the input is less than the length, and return the string when input is greater.

Example:

$length = 10;
$char = 0;
$type = 'd';
$format = "%{$char}{$length}{$type}"; // or "$010d";

//print and echo
printf($format, 987654321);

//store to a variable
$newFormat = sprintf($format, 987654321);

// output: 0987654321

In the example, the fixed length is set to 10 and the input length is 9, so it adds one zero in the left if using printf()/sprintf.

sprintf() Parameter Values

Parameter Description
format (Required) The string and how to format the variables.
Possible format values:
%% - Percent sign
%b - Binary
%c - Character referenced to ASCII
%d - decimal number (negative or positive)
%e - Lowercase scientific notation
%E - Uppercase scientific notation
%u - Unsigned decimal number
%f - Float number (local settings aware)
%F - Float number (not local settings aware)
%g - shorter version of %e and %f
%G - shorter version of %E and %F
%o - Octal
%s - String
%x - Hexadecimal (lowercase)
%X - Hexadecimal (uppercase)
arg1 (Required) To be inserted at the first %-sign
``arg2 (Optional) To be inserted at the second %-sign
argg++ (Optional) To be inserted at the third, fourth, etc. %-sign

Note:

  • If the input string length is greater than or equal to the pad length, it will only return the string - no characters will be omitted.
  • Padding is only added the length of the input is less than the padding length.

str_pad() to add leading zeros in PHP

This method will pad a string to a new length of specified characters.

Example:

$length = 7;
$string = "12345";
echo str_pad($string,$length,"0", STR_PAD_LEFT);
//output: 0012345

The example above will add the zero to the specified string until it matches the specified length (which is 7 in this case).

str_pad() Parameters List

Parameter Description
string The string to pad
length Specifies the new length of the string. **Note: **If the value is less than the length of the string, nothing will happen.
pad_string Specifies the string to use for padding. The default value is whitespace.
pad_type Specifies where to pad the string.
Accepted Values:
STR_PAD_BOTH - This will pad both sides of the string.
STR_PAD_LEFT - Pad the left side of the string
STR_PAD_RIGHT - Pad to the right side of the string

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