How to calculate numbers with comma?

Look into the number format functions. And are you sure this isn't stored as a string?

The field is a string. What should it be to allow for commas?

Why not store currency as integers in their lowest form, for example £100 would be 10000pence = 10000.

If you have a decimal value use decimal field, it's for this case.

Okey, so I've tried using decimal field, but when trying this in Sequel Pro I get the following error:

The row was not written to the MySQL database. You probably haven't changed anything. Reload the table to be sure that the row exists and use a primary key for your table.

My field looks like this: Field: price Type: decimal Length: 11,0 Default: 0

because you have a string with commas. I'm not sure how, but you have to set the locale so that php knows that the comma is decimal notation.

check http://php.net/manual/en/class.numberformatter.php

Again learn string functions. Could even be done in JavaScript.

@eriktobben

My field looks like this: Field: price Type: decimal Length: 11,0 Default: 0

that's not correct for what you want to achieve. You have to use eg 8,3 as length for your decimal field, which means the number can be a total of 8 digits and there are 3 digits on the right side of the comma, eg 12350,750

@frezno Ahh, now I get it! Thanks!

My problem now is that it wont take comma, but accepts period. Is this easy to fix on database end, or should I just replace commas with periods when writing to db and replace them back, when editing?

use numberformatter, it is what it's for

@eriktobben

the input to your database has to be using a period. The number will be displayed according to your local setting though.

For the output in your programm you can write a little helper function to make things easier. Something like that:

/**
 * Format the price and add the currency symbol
 *
 * @param int $price
 * @param string $currency
 * @param int $post
 *
 * @return string
 */
function format_price($price, $currency = '€', $post = 1)
{
    if ($post === 1)
    {
        $formatted_price = number_format($price, 2, ',', '.') . ' ' . $currency;
    } else {
        $formatted_price = $currency.number_format($price, 2);
    }

    return $formatted_price;
}

check example 2 of numberformatter parse method

http://php.net/manual/en/numberformatter.parse.php

this will convert eg 1.234,56 into 1234.56 which you can then store in a decimal column or you can multiply by 100 and store as integer pence/cents

Thank you all for helping me on this, it works perfectly!