PHP 7.0.6 Released

    gmp_setbit

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

    gmp_setbit — Set bit

    Description

    void gmp_setbit ( GMP &$a , int $index [, bool $bit_on = true ] )

    Sets bit index in a.

    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).

    Return Values

    A GMP number resource in PHP 5.5 and earlier, or a GMP object in PHP 5.6 and later.

    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.

    See Also

    User Contributed Notes

    bluej100@gmail
    8 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
    ?>
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