División de variables en el redondeo de PHP

I have a simple calculator script for making calculations of facebook insights.

There is a function in my script called fb_growth where I pass two arguments in: one for the current month's data ($moc) and one for the previous month's data ($mop) and I am trying to find the growth percentage (positive or negative) between the 2. Here is my function script:

//Growth Calculator Function
function fb_growth($moc, $mop) {
    if($moc>=$mop) {
        $grp = ($moc/$mop);
        $grf = ($grp - 1);
        return $grf;
    else if($moc<$mop) {
        $grp = ($mop/$moc);
        $grf = (1 - $grp);
        return $grf;

The values I enter in are coming from a form that the user fills out. In this particular case, the numbers passed in are fb_growth($fbfi1, $fbfi2); where $fbfi1 equals the string '1719223' and $fbfi2 equals the string '1859867'. In this case, $moc is less than $mop, so 1719223 gets divided by 1859867, which should return 1.08180672315, but instead it returns 1, which then gets subtracted by 1 to get 0. What I want to end up with is '-.08180672315', which would be my growth percentage, but I cannot get it to give me this outcome. If I echo ("1859867"/ "1719223"); then I get 1.08180672315, but when the strings are held in the variables and I echo ("$fbfi2" / "$fbfi1"); then I get 1.

I tried settype() to a double and an int for $grf and for both $fbfi1 & 2 and same result. If I set $grf as a global and echo gettype(), it will give me the double or the int, but I still get the same value: 0. Is there something I can adjust in my php settings for this, or is there something wrong with my setup? I can't find any documentation. Help is MUCH appreciated, thank you!!

preguntado el 10 de marzo de 12 a las 12:03

2 Respuestas

PHP does automatic casting, see the type juggling manual. Integer division yields integer result (hence the 1).

Cast the values before doing arithmetic calculations: (float) $var

respondido 10 mar '12, 12:03

Okay so I have casted $fbfi1 and 2 floats with (float) $fbfi1 = $_POST['pvm1']; where it is setting the value from the form, as well as casting $grp and $grf as floats in the function, but I am still getting the same result. - Dante Cullari

My code now looks like this //Growth Calculator Function function fb_growth($moc, $mop) { if($moc>=$mop) { (float) $grp = ($moc/$mop); (float) $grf = ($grp - 1); return $grf; } elseif($moc<$mop) { (float) $grp = ($mop/$moc); (float) $grf = (1 - $grp); return $grf; } } with the code from the above comment also for the arguments passed in - Dante Cullari

you're still doing integer divison. one of the operands must be float. - karoly horvath

And the problem was... comma's in the entry numbers!! I was inputing 123,456 instead of 123456. That's what you get when you just carelessly copy and paste sometimes..wow. Thanks for all the help though, I learned a lot about casting!

Respondido el 06 de junio de 12 a las 15:06

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