PHP remainder (modulo) operation

This article mainly introduces the remainder (modulus) operation in PHP, which has a certain reference value. Now I share it with everyone. Friends in need can refer to it

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Let’s look at the next small case first:

    $n = 8.45;
    $result = $n*100;
    echo gettype($result);
    var_dump($result);
    echo intval($n*100).&#39;<br>&#39;;
    echo $result%100;

Output:

double
float 845
844
44

Are you a little surprised to see this result?

In fact, the essence is intval((double) 845) = 944; because we used asking for remainder (modulo) operator %, while the operands of the modulo operator will be converted to integers (except for the decimal part) before operation.

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In addition, the result of the modulo operator % is the same as the sign (sign) of the dividend. That is, $a (dividend) % $b (divisor) has the same sign as the result. Let’s look at a few examples:

Such as:

    echo (5 % 3)."\n";           
    echo (5 % -3)."\n";       
    echo (-5 % 3)."\n";          
    echo (-5 % -3)."\n";

Output:

2 2 -2 -2

Let's introduce another Math function related to remainder fmod(). This function mainly returns the floating point remainder of division.

float fmod ( float $x , float $y )

返回被除数（x）除以除数（y）所得的浮点数余数。余数（）的定义是：x = i * y + r，其中 是整数。如果 y 是非零值，则 和 x 的符号相同并且其数量值小于 y。 其实实质就是x/y的浮点数余数。

例子：

$x = 5;
$y = 2;
// $t = mod($x, $y);//Fatal error: Call to undefined function mod()
echo '我是fmod($x, $y)输出的值：'.fmod($x, $y);
echo "<br>";
echo &#39;我是$x % $y输出的值：&#39;.$x % $y;

结果：

我是fmod($x, $y)输出的值：1

我是$x % $y输出的值：1

    $x = 5.8;
    $y = 2.5;
    // $t = mod($x, $y);//Fatal error: Call to undefined function mod()
    echo '我是fmod($x, $y)输出的值：'.fmod($x, $y);
    echo "<br>";
    echo &#39;我是$x % $y输出的值：&#39;.$x % $y;

结果：

我是fmod($x, $y)输出的值：0.8

我是$x % $y输出的值：1

注意的是，PHP里并没有mod()函数，使用时应注意。

小结：

1、%求余的时候，就是先把运算之前的被除数和除数都转换成整数（除去小数部分）

2、fmod()就类似于数学里面的求余运算。

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