如何将销售价格舍入到第一个十进制数字？

Question

I am using woocommerce 3.5.3 and Woocommerce All Discounts plugin from Orion. After I am applying the discounts. The prices look like this: €59.90 -> €47.92, €69.90 -> €55.92. etc.

How can I round it to the first decimal digit?

I have already tried a few solutions but none work. For example:

function round_price_product( $price ){
    // Return rounded price
    return round( $price );
}

Answer 1

If we split the price in integers and fractions then we can round the fractions and use str_pad to make sure we don't loose a digit (47.9 instead of 47.90)

Because we divide the fraction with 10 we get a new fraction that can be rounded with zero precision.
Then multiply it with 10 to get it "back" as originally.

function round_price_product( $price ){
    // Return rounded price
    $parts = explode(".", $price);
    $parts[1] = round($parts[1]/10,0)*10;
    if($parts[1] == 100) { // round up to next integer
        $parts[0]++;
        $parts[1] = 0;
    }
    return $parts[0] . "." . str_pad($parts[1], 2, 0, STR_PAD_RIGHT);
}

echo round_price_product("47.92"); //47.90
// 47.95 -> 48.00
// 47.02 -> 47.00

https://3v4l.org/92sO1