PHP Manual: Bitwise OR

GMP gmp_or(GMPintstring $num1, GMPintstring $num2)

Calculates bitwise inclusive OR of two GMP numbers.

num1: A GMP object, an int, or a string that can be interpreted as a number following the same logic as if the string was used in gmp_init with automatic base detection (i.e. when base is equal to 0).
num2: A GMP object, an int, or a string that can be interpreted as a number following the same logic as if the string was used in gmp_init with automatic base detection (i.e. when base is equal to 0).

A GMP object.

Example #1 gmp_or example

<?php
$or1 = gmp_or("0xfffffff2", "4");
echo gmp_strval($or1, 16) . "\n";
$or2 = gmp_or("0xfffffff2", "2");
echo gmp_strval($or2, 16) . "\n";
?>

The above example will output:

fffffff6
fffffff2