# gmp_clrbit

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

gmp_clrbit — Clear bit

### 说明

gmp_clrbit(GMP `$num`, int `$index`): void

Clears (sets to 0) bit `index` in `num`. The index starts at 0.

### 参数

`num`

  A GMP object.

`index`

  The index of the bit to clear. Index 0 represents the least significant bit.

### 返回值

没有返回值。

### 示例

示例 #1 gmp_clrbit() example

`<?php
$a = gmp_init("0xff");
gmp_clrbit($a, 0); // index starts at 0, least significant bit
echo gmp_strval($a) . "\n";
?>`

以上示例会输出：

    254

### 注释

> 注意:

> Unlike most of the other GMP functions, gmp_clrbit() must be called with a GMP object that already exists (using gmp_init() for example). One will not be automatically created.

### 参见

- gmp_setbit() - Set bit
- gmp_testbit() - Tests if a bit is set

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