(PHP 5 >= 5.3.0)
gmp_testbit — Tests if a bit is set
Tests if the specified bit is set.
It can be either a GMP number resource, or a numeric string given that it is possible to convert the latter to a number.
The bit to test
如果成功则返回 TRUE，失败则返回 FALSE。
E_WARNING is issued when index is less than zero.
Example #1 gmp_testbit() example
<?php
$n = gmp_init("1000000");
var_dump(gmp_testbit($n, 1));
gmp_setbit($n, 1);
var_dump(gmp_testbit($n, 1));
?>
上例将输出：
bool(false) bool(true)