- var_dump: documentation ( source)
- setlocale: documentation ( source)
<?php
setlocale(LC_ALL, 'de_DE.UTF-8');
$num = '123,456';
$num = (float)$num;
var_dump( $num );
$fmt = new NumberFormatter( 'en_US', NumberFormatter::DECIMAL );
echo $fmt->parse($num)."\n";