(PHP 4 >= 4.0.4, PHP 5, PHP 7)
gmp_sign — Sign of 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";
?>
The above example will output:
1 -1 0