PHP bitwise OR vs Javascript bitwise OR

Question

Javascript:

var a=209348540618090 | 0;//-1050290838

PHP:

$a= 209348540618090|0;//209348540618090
$a=(209348540618090 & 0xffffffff) | 0;  //3244676458

Why is the result of the bitwise operation in PHP different to the bitwise operation in Javascript?

Answer 1

Bitwise operators operate on 32-bit integers in JavaScript. Here's how it converts the integer before applying the OR operator:

1. Take 209348540618090 modulus 2^32. Result is 3244676458.
2. Since 3244676458 is greater than 2^31 = 2147483648, substract 2^32. Result is -1050290838.
3. Bitwise OR -1050290838 and 0, result is -1050290838.

Reference on how JS converts the number to a 32-bit integer: https://tc39.es/ecma262/multipage/abstract-operations.html#sec-toint32

On the other hand, the PHP example simple applies bitwise OR to the binary representation of the operands, which result in 3244676458.