gmp_sign

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

gmp_sign — Sign of number

Description

int gmp_sign ( GMP $a )

Checks the sign of a number.

Parameters

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 a number.

Return Values

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

Examples

Example #1 gmp_sign() example


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

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

// zero
echo gmp_sign("0") . "\n";
?>

The above example will output:

1
-1
0

User Contributed Notes

thomas at zilliox dot me

4 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.

jdyerjdyer

5 months 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

web-develop at yandex dot ru

2 months ago


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

krees

2 years ago


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

Andrew Martin

1 year ago


Another way for those without GMP:

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

gri501r at yandex dot ru