PHP sprintf() returning wrong value for %02

daymobrew

I wrote code for WooCommerce to superscript the decimal number.
It was simple enough, split out the price into unit and decimal, wrap 'sup' tags around decimal and concatenate both numbers again.

Someone said that it didn't work for some numbers e.g. 28.95 rendered as 28.94!

I tracked it down to a bizarre issue with sprintf(). I am using PHP 7.1.11 via XAMPP on Windows 7.

[PHP]<?php

foreach ( array( 28.91, 28.92, 28.93, 28.94, 28.95, 28.96, 28.97 ) as $price ) {
$unit = intval( $price );
$decimal = ( $price - intval( $price ) ) * 100;
$decimal = sprintf( '^%02d', $decimal );

echo $price, ' - ', $unit . $decimal, "\n";
}[/PHP]

The result:

28.91 - 28<sup>91</sup>
28.92 - 28<sup>92</sup>
28.93 - 28<sup>92</sup>
28.94 - 28<sup>94</sup>
28.95 - 28<sup>94</sup>
28.96 - 28<sup>96</sup>
28.97 - 28<sup>96</sup>

What's going on???

Talisman

You're dealing with floating point and sprintf is not a rounding function.

echo number_format(28.96, 16);
28.9600000000000009

echo number_format(28.97, 16);
28.9699999999999989

If you take away 28 and multiply by 100 the first 2 didgits are 96 in both cases.

You have two options:

1 - Use round

$decimal = round(( $price - intval( $price ) ) * 100);

2 - Stick with strings

foreach ( array( 28.91, 28.92, 28.93, 28.94, 28.95, 28.96, 28.97 ) as $price ) {
    $parts = explode( '.', strval( $price ));
    echo $price, ' - ', $parts[0] . '<sup>' . $parts[1] . '</sup>' , "\n";
}

daymobrew

Thanks.
I'll go with round() as I want to keep the code generic without hard coding the decimal separator (which could change) - the original function receives 5 parameters:
- formatted price (a string with localised thousands and decimal separators)
- price (floating point number)
- number of decimal places (generally 2 but could be more or less)
- decimal separator
- thousands separator

Talisman

You can always query the locale to find out the separators.

setlocale(LC_ALL, 'en_IE');
$locale_info = localeconv();
print_r($locale_info);

Output:

Array
(
    [decimal_point] => .
    [thousands_sep] => ,
    [int_curr_symbol] => EUR
    [currency_symbol] => €
    [mon_decimal_point] => .
    [mon_thousands_sep] => ,
    [positive_sign] =>
    [negative_sign] => -
    [int_frac_digits] => 2
    [frac_digits] => 2
    [p_cs_precedes] => 1
    [p_sep_by_space] => 0
    [n_cs_precedes] => 1
    [n_sep_by_space] => 0
    [p_sign_posn] => 1
    [n_sign_posn] => 1
    [grouping] => Array
        (
            [0] => 3
            [1] => 3
        )

    [mon_grouping] => Array
        (
            [0] => 3
            [1] => 3
        )

)

You can pull the individual elements that you need out of the associative array.

echo $locale_info['decimal_point'];
.

echo $locale_info['thousands_sep'];
,

daymobrew

The code is for a WooCommerce site and the site admin sets the separators (which will probably match the locale settings).