That is because you re hitting the ** MAXIMUM INTEGER LIMIT** which is

`2147483647`

## From the PHP Docs…

The maximum value depends on the system. 32 bit systems have a maximum

signed integer range of -2147483648 to 2147483647. So for example on

such a system, intval(‘1000000000000’) will return 2147483647. The

maximum signed integer value for 64 bit systems is

9223372036854775807.

Thus to handle such big integers you need to make use of an extension like `(GMP) GNU Multiple Precision`

```
<?php
$v1="6463334891";
$v2="1000212390";
$a = gmp_init($v1);
$b = gmp_init($v2);
echo gmp_intval($a) ^ gmp_intval($b); //"prints" 7426059853
```

Else , Switch to a `64-bit system.`

solved PHP XOR operation two numbers