(PHP 4 >= 4.0.4, PHP 5)
gmp_sign — Sign of number
Checks the sign of a number.
It can be either a GMP number resource, or a numeric string given that it is possible to convert the latter to a number.
Returns 1 if a is positive, -1 if a is negative, and 0 if a is zero.
Example#1 gmp_sign() example
<?php
// positive
echo gmp_sign("500") . "\n";
// negative
echo gmp_sign("-500") . "\n";
// zero
echo gmp_sign("0") . "\n";
?>
上例将输出：
1 -1 0