What's the best way to validate numbers with comma as decimal separator?

Question

In a Laravel app, I have a form on which I need to validate numbers with a comma as the decimal separator. For the moment, it only works with a point because my validation rule is:

$rules = [
    'amount' => 'numeric|min:0',
];

What’s the best method :

• Keep the rule and replace comma with point before validation ? Is there a before_validation observer or something like this ?
• Build a custom validation rule ? french_numeric for example ?

Answer 1

Laravel supports regex pattern in validation rule so you can use the given pattern to match something like 12,365.00 and it's recommended to use an array instead of pipe when using regular expressions as a rule

$rules = array('amount' => array('match:/^[0-9]{1,3}(,[0-9]{3})*\.[0-9]+$/'));

Check this link. Also, if you want to remove the commas for any reason then check this answer.

Answer 2

Building on the excellent answer from The Alpha, here is a code snippet to make a float validation configurable.

Add this snippet to the boot() function in your AppServiceProvider class (tested with Laravel 5.4):

Validator::extend('float', function ($attribute, $value, $parameters, $validator) {
    $thousandsSeparator = env('APP_NUMBER_THOUSANDS_SEPARATOR') == '.' ? '\\' . env('APP_NUMBER_THOUSANDS_SEPARATOR') : env('APP_NUMBER_THOUSANDS_SEPARATOR');
    $commaSeparator = env('APP_NUMBER_COMMA_SEPARATOR') == '.' ? '\\' . env('APP_NUMBER_COMMA_SEPARATOR') : env('APP_NUMBER_COMMA_SEPARATOR');
    $regex = '~^[0-9]{1,3}(' . $thousandsSeparator . '[0-9]{3})*' . $commaSeparator . '[0-9]+$~';
    $validate = preg_match($regex, $value);

    if ($validate === 1) {
        return true;
    }

    return false;
});

Your .env-file would have those two lines:

APP_NUMBER_COMMA_SEPARATOR="."
APP_NUMBER_THOUSANDS_SEPARATOR=","

And your rule would look like this:

$rules = [
    'amount' => 'float|min:0',
];

Note: I'm only escaping the . correctly. If you are going to use charaters that have special meaning in regex syntax (like * or +) you have to escape them too.

But since a float number like 550*345,00 (550,345.00) or 57+44 (57.44) wouldn't make sense I've ignored this issue.

Kind regards