Signed Integer
PHP integers are always signed. They use one bit to represent the sign, allowing both negative and positive values. PHP does not support unsigned integers.
On a 64-bit platform, a PHP integer spans from PHP_INT_MIN, aka -9,223,372,036,854,775,808, or -2^63 to PHP_INT_MAX, aka 9,223,372,036,854,775,807, or 2^63 - 1. On a 32-bit platform, the range is -2^31 to 2^31 - 1.
When an operation would produce a value outside that range, PHP silently promotes the result to a float, which has a larger range but reduced precision for large integers.
Languages such as C or Rust distinguish signed integers int, i64 from unsigned integers uint, u64. PHP makes no such distinction: all integers are signed.
<?php
$max = PHP_INT_MAX; // 9223372036854775807
$min = PHP_INT_MIN; // -9223372036854775808
// Overflow promotes to float silently
$overflow = PHP_INT_MAX + 1; // float(9.2233720368548E+18)
var_dump($overflow); // float, not integer
?>