About hashing passwords with argon2i - php

Question

I set up a dev server and I installed nginx with php-fpm and 7.2 php (I installed all the necessary php packages).
The time has come to upgrade the security of all logins, using the argon2i algo.
So, I tried this (test code in dev enviroment. The security in the code, will come later):
require('connector.php');
$usr_u = $_POST['username'];
$psw_u = $_POST['password'];
$usr = mysqli_real_escape_string($conn, $usr_u);
$psw = mysqli_real_escape_string($conn, $psw_u);
$f_pass = password_hash($psw, PASSWORD_ARGON2I);
$result = "SELECT `username` FROM `users` WHERE username = '$usr'";
$tbl = mysqli_query($conn, $result);
$table = $tbl->fetch_assoc();
$m_user = $table['username'];
if ($m_user == $usr)
{
//correct username
echo 'Correct username!<br>';
$result = "SELECT `password` FROM `users` WHERE username = '$m_user'";
$tbl = mysqli_query($conn, $result);
$table = $tbl->fetch_assoc();
$m_pass = $table['password'];
if (password_verify($m_pass,$f_pass)) //always returns false
{
echo 'Password correct!<br>';
}
else
{
echo 'Wrong password!<br>';
}
}
else
{
echo 'Wrong username!<br>';
}
//close connection
mysqli_close($conn);
I always get "Correct username!" and "Wrong password!". I used echo on hashed password from the DB and from the input and I see that every time the hashed password is different. I assume that the hashing process, include using random salt and there is my issue.
As far as I understand, the random salt is necessary in order to retain the security of the hashing.
Can you please point me to the right direction, on how to solve this? I have the hashed password in my DB and I can't figure out a way to check the input password against the one in my DB (using password_verify and hash_equals).
Thank everyone in advance for the help.

Answer 1

Look at the documentation for password_verify:
bool password_verify ( string $password , string $hash )
The first argument is the password but you are passing it the hash you want to compare it to.
The second argument is the hash you want to compare it to but you are passing it a new hash created from user input.
password_verify($_POST['password'], $m_pass)