This had me scratching my head. When working with certain English locales (e.g. "en_US" and "en_CA" among others but certainly not all), it is important to note that negative numbers are formatted differently between PHP 5.5 and PHP 5.6.
Code:
<?php
$formatter = new NumberFormatter('en_US', NumberFormatter::CURRENCY);
echo $formatter->formatCurrency(-0.99, 'USD'), PHP_EOL;
$formatter = new NumberFormatter('en_CA', NumberFormatter::CURRENCY);
echo $formatter->formatCurrency(-0.99, 'USD'), PHP_EOL;
?>
Output from PHP 5.5:
-$0.99
-US$0.99
Output from PHP 5.6:
($0.99)
(US$0.99)
