PHP: gmp_setbit - Manual (original) (raw)
(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)
gmp_setbit — Set bit
Description
Parameters
num
A GMP object.
index
The index of the bit to set. Index 0 represents the least significant bit.
value
True to set the bit (set it to 1/on); false to clear the bit (set it to 0/off).
Return Values
No value is returned.
Examples
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 0b11 echo gmp_strval($a), ' -> 0b', gmp_strval($a, 2), "\n"; ?>
The above example will output:
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 0 echo gmp_strval($a), ' -> 0b', gmp_strval($a, 2), "\n"; ?>
The above example will output:
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 0 echo gmp_strval($a), ' -> 0b', gmp_strval($a, 2), "\n"; ?>
The above example will output:
255 -> 0b11111111 254 -> 0b11111110
Notes
Note:
Unlike most of the other GMP functions, gmp_setbit() must be called with a GMP object that already exists (usinggmp_init() for example). One will not be automatically created.
Found A Problem?
18 years ago
The third parameter is somewhat confusingly named; it would probably be better described as "$set_state". If true, it sets the bit to 1. If false, it sets the bit to 0. Default is true.
<?php
$num = gmp_init(1);
gmp_setbit($num, 1);
echo 'gmp_setbit(1, 1): '.gmp_strval($num, 2)."\n"; // 11
$num = gmp_init(1);
gmp_setbit($num, 1, true);
echo 'gmp_setbit(1, 1, true): '.gmp_strval($num, 2)."\n"; // 11
$num = gmp_init(1);
gmp_setbit($num, 0, false);
echo 'gmp_setbit(1, 0, false): '.gmp_strval($num, 2)."\n"; // 0
?>