(PHP 4 >= 4.0.4, PHP 5)
gmp_popcount — Population count
Get the population count.
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 population count of a , as an integer.
Example #1 gmp_popcount() example
<?php
$pop1 = gmp_init("10000101", 2); // 3 1's
echo gmp_popcount($pop1) . "\n";
$pop2 = gmp_init("11111110", 2); // 7 1's
echo gmp_popcount($pop2) . "\n";
?>
上例将输出：
3 7