Zero-pad digits in string

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I need to cast single figures (1 to 9) to (01 to 09). I can think of a way but its big and ugly and cumbersome. I'm sure there must be some concise way. Any Suggestions

php
5 Answers

First of all, your description is misleading. Double is a floating point data type. You presumably want to pad your digits with leading zeros in a string. The following code does that:

$s = sprintf('%02d', $digit);

For more information, refer to the documentation of sprintf.

user_19680

There's also str_pad

<?php
$input = "Alien";
echo str_pad($input, 10);                      // produces "Alien     "
echo str_pad($input, 10, "-=", STR_PAD_LEFT);  // produces "-=-=-Alien"
echo str_pad($input, 10, "_", STR_PAD_BOTH);   // produces "__Alien___"
echo str_pad($input, 6 , "___");               // produces "Alien_"
?>
user_165920

The performance of str_pad heavily depends on the length of padding. For more consistent speed you can use str_repeat.

$padded_string = str_repeat("0", $length-strlen($number)) . $number;

Also use string value of the number for better performance.

$number = strval(123);

Tested on PHP 7.4

str_repeat: 0.086055040359497   (number: 123, padding: 1)
str_repeat: 0.085798978805542   (number: 123, padding: 3)
str_repeat: 0.085641145706177   (number: 123, padding: 10)
str_repeat: 0.091305017471313   (number: 123, padding: 100)

str_pad:    0.086184978485107   (number: 123, padding: 1)
str_pad:    0.096981048583984   (number: 123, padding: 3)
str_pad:    0.14874792098999    (number: 123, padding: 10)
str_pad:    0.85979700088501    (number: 123, padding: 100)
user_112714320

Here is my solution to handle both positive and negative numbers

<?php

// add zeros to a number at left or right side.
function add_zeros_to_number( $number, $number_of_zeros, $zeros_position="left"){
    // check if number is negative
    $is_negative = FALSE;
    if ( strpos($number , '-') !== FALSE ){
        $is_negative = TRUE;
        $number = substr($number, 1);
    }
    if($zeros_position == "right"){
        $r = str_pad($number, $number_of_zeros, "0", STR_PAD_RIGHT);
    }else{
        $r = str_pad($number, $number_of_zeros, "0", STR_PAD_LEFT);
    }
    if( $is_negative ){
        return "-".$r;
    }else{
        return $r;
    }
}

// how to use
$number = -333;   // Desire number 
$number_of_zeros = 4;  // number of zeros [ your number length + zeros ]
$position = "right";  // left or right . default left
echo $result = add_zeros_to_number($number, $number_of_zeros, $position);

// output
// -333 => -3330    left
// -333 => -0333    right
user_8890300
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