gmp_sign()

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

Sign of number

说明

gmp_sign(GMP$a): int

Checks the sign of a number.

参数

$a

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 an integer.

返回值

Returns 1 if$ais positive,-1 if$ais negative, and 0 if$ais zero.

范例

gmp_sign() example

<?php
// positive
echo gmp_sign("500") . "\n";
// negative
echo gmp_sign("-500") . "\n";
// zero
echo gmp_sign("0") . "\n";
?>

以上例程会输出：

1
-1
0

参见

• gmp_abs()Absolute value
• abs()绝对值

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.

Using a spaceship in PHP7:
<?php
$sign = $number <=> 0;
?>

Just
$sign = ($a==0 ?0 :$a/abs($a));

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

You can also do this:
<?php
$sign = min(1, max(-1, $a));
?>

Another way for those without GMP:
<?php
function sign($number) {
  return $number / abs($number ?: 1);
}
?>

May be it's bug :
   gmp_sign(1) returns 'false'