How do I format a number to a dollar amount in PHP

PHP also has money_format().

Here's an example:

echo money_format('$%i', 3.4); // echos '$3.40'

This function actually has tons of options, go to the documentation I linked to to see them.

Note: money_format is undefined in Windows.

UPDATE: Via the PHP manual: https://www.php.net/manual/en/function.money-format.php

WARNING: This function [money_format] has been DEPRECATED as of PHP 7.4.0. Relying on this function is highly discouraged.

Instead, look into NumberFormatter::formatCurrency.

    $number = "123.45";
    $formatter = new NumberFormatter('en_US', NumberFormatter::CURRENCY);
    return $formatter->formatCurrency($number, 'USD');

The easiest answer is number_format().

echo "$ ".number_format($value, 2);

If you want your application to be able to work with multiple currencies and locale-aware formatting (1.000,00 for some of us Europeans for example), it becomes a bit more complex.

There is money_format() but it doesn't work on Windows and relies on setlocale(), which is rubbish in my opinion, because it requires the installation of (arbitrarily named) locale packages on server side.

If you want to seriously internationalize your application, consider using a full-blown internationalization library like Zend Framework's Zend_Locale and Zend_Currency.

You can just do:

string.Format("{0}", yourDouble);

It will include only digits when necessary.

If you want other examples of formatting doubles to string check out this link.

EDIT: Based on your comment you want the , seperator so you could do:

string.Format("{0:0,0.########}", yourDouble);

Just put as many # for the max number of decimal places you want to show. It will only show the digits when necessary but up to the maximum digits based on how many # you include in the format. The # means only show a digit if necessary so if you give a number like 123 with no decimal, it will display as 1,234 but if you give it 1234.456, it will display as 1,234.456. If you go beyond the max digits you specified they will be rounded.

EDIT: To fix your double zero scenario just change it to:

string.Format("{0:#,0.########}", yourDouble);

That should work perfectly now :)