Description:
------------
---
From manual page: http://www.php.net/function.password-hash
---

The manual page says:
"memory_cost (integer) - Maximum memory (in bytes) that may be used to compute the Argon2 hash. Defaults to PASSWORD_ARGON2_DEFAULT_MEMORY_COST."

The memory in reality is in kilobytes, not bytes. Confirmed by testing the memory usage, execution speed and also by reading the source code.

Test script:
---------------
password_hash('passu', PASSWORD_ARGON2I, [
    'memory_cost' => 1024 * 1024, // According to documentation, should be 1MB
    'time_cost' => 4,
    'threads' => 2,
]);

Expected result:
----------------
Check the memory usage of the script. It's 1GB.

Actual result:
--------------
Memory usage should not be a lot more than 1MB.