In a previous post, I wrote about the usage of the date_i18n function in WordPress called date_i18n Function Reference and Usage.
This post will address how to properly format displaying values (numbers) according to the WordPress blog settings.
The function to use for this is number_format_i18n – Read the reference material on wordpress.org
WordPress comes with a lot of nice features to reduce developer headaches and ensure things just work no matter where you use your code.
The usage is much easier than the date-function, as it is a simple function that accepts only a single parameter, the value to be displayed.
$thenumber = 1420.3321; echo number_format_i18n($thenumber,2);
The output will display the number in the correct localized format for your blog, use the second parameter to set the number of decimals.
Edit: Finally, after Brent made a comment back in 2009, I have updated the post to mention decimals.