array_sum() is showing the math

Question

I am trying to calculate how much the commission is off of an array I am pulling from an API. The following is my code.

$mst_per_off_base=   $pri['base']  * '.01'; // calculate 1% of the base price
$gr[] = $pri['com'] - $mst_per_off_base ; // deduct the 1% off of the com
echo array_sum($gr); // total of all after deduction

$pri['base'] and $pri['com'] represent more than one number. The problem is that it is showing the math.

For example, if $gr equals 50.85 then it is echoing 50.85101.7152.55 I would like it just to just show 152.55.

Any suggestion?

You can't just do math *at* an array like that, and beside that you absolutely **should not** use floating point numbers to represent currency unless you're ok with straight up losing money. 1. Use something like [moneyphp](https://packagist.org/packages/moneyphp/money). 2. Use a loop to do the math against each *item* in the arrays, not the arrays themselves. — Sammitch, Feb 13 '18 at 20:05
If that's real code you should be getting: _Notice: Use of undefined constant mst_per_off_base - assumed 'mst_per_off_base'_ — AbraCadaver, Feb 13 '18 at 20:12
Possible duplicate of [Is floating point math broken?](https://stackoverflow.com/questions/588004/is-floating-point-math-broken) — , Feb 13 '18 at 20:16
@rtfm It is broken but I suspect this issue has more to do with using strings in equations but it doesn't feel worthwhile to test and verify given the limited amount of info provided in the question. — MonkeyZeus, Feb 13 '18 at 20:23
Is this code in a loop? I think you're just seeing the `echo` that it does each time through the loop. — Barmar, Feb 13 '18 at 20:26
There's simply no way that `echo array_sum(...)` will echo more than one number. — Barmar, Feb 13 '18 at 20:27
The OP code is incomplete -- needs to show where $pri defined and takes on a value. — slevy1, Feb 13 '18 at 20:27

MonkeyZeus · Answer 1 · 2018-02-13T20:19:41.957

2

It's bad enough to try and natively perform math calculations with floats, it's double-ly (pun, ha, get it?) bad to interleave strings into your equations.

You need PHP's bcmath.

Look into bcmul() and bcadd() in particular.

edited Feb 13 '18 at 20:19

answered Feb 13 '18 at 20:07

MonkeyZeus

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slevy1 · Answer 2 · 2018-02-13T20:49:43.923

Here's an illustration of what needs to happen:

<?php

// suppose:
$pri['base'] = 30000;
$pri['com'] = 5000;

// then
$mst_per_off_base =   bcmul($pri['base'],.01); // calculate 1% of the base price
$gr[] = bcsub($pri['com'],$mst_per_off_base); // deduct the 1% off of the com
echo array_sum($gr); // total of all after deduction

I had to correct the OP code. "mst_per_off_base" needed to be prepended with a dollar sign. And, this was a case of subtraction, so use bcsub() and not bcadd (unless you wish to add a negative number with a positive one). Lastly, it's extremely important to include as complete an example as is necessary for the code to run correctly. So, I defined $pri myself to pose a theoretical example.

See live code

score 0 · Accepted Answer · answered Feb 13 '18 at 20:35

0

@bamar is correct I accidentally nested it in a loop.

Thank you for all of your suggestions regarding the proper way to do the math I have some reading to do...

answered Feb 13 '18 at 20:35

A Kaufman

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5

array_sum() is showing the math

3 Answers3