PHP Rounding Numbers

Question

I cannot seem to figure out how to always round up in PHP. ceil() would be the obvious choice but I need the same functionality that round() provid

Answer 1

As version ceil(pow(10, $precision) * $value) / pow(10, $precision); fails in some cases, e.g. round_up(2.22, 2) gives incorrect 2.23 as mentioned here, so I have adapted this string solution for round_down() to our round_up() problem. This is the result (a negative precision is not covered):

function round_up($value, $precision) {        
    $value = (float)$value;
    $precision = (int)$precision;
    if ($precision < 0) { 
        $precision = 0;
    }
    $decPointPosition = strpos($value, '.');
    if ($decPointPosition === false) { 
        return $value;
    }
    $floorValue = (float)substr($value, 0, $decPointPosition + $precision + 1);
    $followingDecimals = (int)substr($value, $decPointPosition + $precision + 1);
    if ($followingDecimals) {
        $ceilValue = $floorValue + pow(10, -$precision); // does this give always right result?
    }
    else {
        $ceilValue = $floorValue;
    }
    return $ceilValue;                
}

I don't know it is bulletproof, but at least it removes the above mentioned fail. I have done no binary-to-decimal-math-analysis but if $floorValue + pow(10, 0 - $precision) works always as expected then it should be ok. If you will find some failing case let me know - we should look for another solution :)