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Parameters
-
a -
The value to modify.
Either a GMP number resource in PHP 5.5 and earlier, a GMP object in PHP 5.6 and later, or a numeric string provided that it is possible to convert the latter to a number.
-
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).
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:
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 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 resource that already exists (using gmp_init() for example). One will not be automatically created.
English translation
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Document created the 30/01/2003, last modified the 26/10/2018
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References
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