Derived from this question : (Java) How does java do modulus calculations with negative numbers?

Anywhere to force PHP to return positive 51?

**update**

Looking for a configuration setting to fix, instead hard-guessing

Or other math function like bcmath?

**updated**

Not entire convinced by that java answer, as it does not take account of negative modulus

`-13+(-64) =?`

## Here is Solutions:

We have many solutions to this problem, But we recommend you to use the first solution because it is tested & true solution that will 100% work for you.

### Solution 1

Anyway, the post you referenced already gave the correct answer:

```
$r = $x % $n;
if ($r < 0)
{
$r += abs($n);
}
```

Where $x = -13 and $n = 64.

### Solution 2

If GMP is available, you can use `gmp_mod`

Calculates n modulo d. The result is always non-negative, the sign of d is ignored.

Example:

```
echo gmp_strval(gmp_mod('-13', '64')); // 51
```

Note that `n`

and `d`

have to be GMP number resources or numeric strings. Anything else won’t work¹

```
echo gmp_strval(gmp_mod(-13, 64));
echo gmp_mod(-13, 64);
```

will both return -51 instead (which is a bug).

**¹** ^{running the above in this codepad, will produce 51 in all three cases. It won’t do that on my development machine.}

### Solution 3

The modulo operation should find the remainder of division of a number by another. But strictly speaking **in most mainstream programming languages the modulo operation malfunctions if dividend or/and divisor are negative**. This includes PHP, Perl, Python, Java, C, C++, etc.

Why I say malfunction? Because according to mathematic definition, **a remainder must be zero or positive**.

The simple solution is to handle the case yourself:

```
if r < 0 then r = r + |divisor|;
```

|divisor| is the absolute value of divisor.

Another solution is to use a library (as @Gordon pointed). However I wouldn’t use a library to handle a simple case like this.

### Solution 4

I hate using `if`

in this case when you can calculate it right away.

```
$r = ($x % $n + $n) % $n;
```

when `$n`

is positive.

### Solution 5

The PHP manual says that

The result of the modulus operator % has the same sign as the dividend — that is, the result of $a % $b will have the same sign as $a. For example

so this is not configurable. Use the options suggested in the question you linked to

**Note: Use and implement solution 1 because this method fully tested our system.Thank you 🙂**

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