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    gmp_sign

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

    gmp_sign — Sign of number

    说明

    gmp_sign(GMP|int|string $num): int

    Checks the sign of a number.

    参数

    num

    Either a GMP object, or a numeric string provided that it is possible to convert the latter to an int.

    返回值

    Returns 1 if num is positive, -1 if num is negative, and 0 if num is zero.

    示例

    示例 #1 gmp_sign() example

    <?php
    // positive
    echo gmp_sign("500") . "\n";

    // negative
    echo gmp_sign("-500") . "\n";

    // zero
    echo gmp_sign("0") . "\n";
    ?>

    以上示例会输出：

    1
-1
0

    参见

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    User Contributed Notes 6 notes

    up
    18
    thomas at zilliox dot me
    13 years ago
    Hi !

    If you don't have the GMP extension, the sign function is really simple to code.
    Here an example of implementation :

    <?php
    function sign( $number ) {
        return (     $number > 0 ) ? 1 : ( ( $number < 0 ) ? -1 : 0 );
    }

    echo     sign( 500 ); // Return 1
    echo sign( -500 ); // Return -1
    echo sign( 0 ); // Return 0
    ?>

    Thomas.
    up
    11
    Andrew Martin
    7 years ago
    Using a spaceship in PHP7:

    <?php
    $sign     = $number <=> 0;
    ?>
    up
    -5
    jdyerjdyer
    8 years ago
    For conciseness or golfing ;)

    $s=$n<0|-($n>0)

    where $s sign is 1 if positive, -1 if negative, otherwise -0 or +0 which is still 0
    up
    -5
    Andrew Martin
    10 years ago
    Another way for those without GMP:

    <?php
    function sign($number) {
        return     $number / abs($number ?: 1);
    }
    ?>
    up
    -9
    krees
    10 years ago
    You can also do this:
    <?php
    $sign     = min(1, max(-1, $a));
    ?>
    up
    -9
    gri501r at yandex dot ru
    10 years ago
    May be it's bug :
         gmp_sign(1) returns 'false'
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