Php/docs/function.gmp-setbit
gmp_setbit
(PHP 4 >= 4.0.4, PHP 5, PHP 7)
gmp_setbit — Set bit
参数
a
The value to modify.
PHP 5.5 之前为 GMP 数值资源,PHP 5.6 之后为 GMP 对象或数字,或可以转为数字的字符串。
index
The index of the bit to set. Index 0 represents the least significant bit.
bit_on
True to set the bit (set it to 1/on); false to clear the bit (set it to 0/off).
范例
Example #1 gmp_setbit() example - 0 index
<?php$a = gmp_init("2"); //echo gmp_strval($a), ' -> 0b', gmp_strval($a, 2), "\n";gmp_setbit($a, 0); // 0b10 now becomes 0b11echo gmp_strval($a), ' -> 0b', gmp_strval($a, 2), "\n";?>
以上例程会输出:
2 -> 0b10 3 -> 0b11
Example #2 gmp_setbit() example - 1 index
<?php$a = gmp_init("0xfd");echo gmp_strval($a), ' -> 0b', gmp_strval($a, 2), "\n";gmp_setbit($a, 1); // index starts at 0echo gmp_strval($a), ' -> 0b', gmp_strval($a, 2), "\n";?>
以上例程会输出:
253 -> 0b11111101 255 -> 0b11111111
Example #3 gmp_setbit() example - clearing a bit
<?php$a = gmp_init("0xff");echo gmp_strval($a), ' -> 0b', gmp_strval($a, 2), "\n";gmp_setbit($a, 0, false); // clear bit at index 0echo gmp_strval($a), ' -> 0b', gmp_strval($a, 2), "\n";?>
以上例程会输出:
255 -> 0b11111111 254 -> 0b11111110
注释
Note:
Unlike most of the other GMP functions, gmp_setbit() must be called with a GMP resource that already exists (using gmp_init() for example). One will not be automatically created.