gmp_popcount

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

gmp_popcountPopulation count

Description

gmp_popcount(GMP|int|string $num): int

Get the population count.

Parameters

num

A GMP object, an int or a numeric string.

Return Values

The population count of num, as an int.

Examples

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";
?>

The above example will output:

3
7

add a note add a note

User Contributed Notes 1 note

up
0
phpmanual at headbank dot co dot uk
5 years ago
If you don't have gmp extension enabled (or don't want to use it for any reason), you can get popcount of an int using decbin() and substr_count().

<?php
$int1
= 133;
$bin1 = decbin($int1); // "10000101"
echo substr_count($bin1, "1");

// Result: 3
?>

Being a string-comparison this is far less efficient than gmp_popcount() (for which there is a dedicated instruction on most if not all modern processors), but may be handy if gmp is unavailable, or in non-performance-critical code that doesn't otherwise need it.
To Top