why 1024 * 1024 * 1024 * 1024 * 1024 returns float?

Question

<?php
$i = 1024 * 1024 * 1024 * 1024 * 1024;
var_dump($i);

output => float(1125899906842600)

why output is a float type ?

Answer 1

If PHP encounter an overflow, it will cast to float.

See http://php.net/manual/en/language.types.integer.php