SHA256 Hashing with Salt in PHP not same as in C#-CodePudding

So I got an ASP.NET web app which uses hashing with salt to store password in mysql database. I am now trying to allow user to login with the same credentials as my web app through a php website. I used the following code to compare user input and hash in php

$pw = $salt . $extpassword;
if (!mb_check_encoding($pw, 'UTF-8')) {
    $pw = mb_convert_encoding($pw, 'UTF-8');
}

return ($fromdb == base64_encode(hash('sha256',$pw, true)));

As for my code in c# used to generate hash:

System.Security.Cryptography.SHA256Managed sha256 = new System.Security.Cryptography.SHA256Managed();
byte[] hash = sha256.ComputeHash(System.Text.Encoding.UTF8.GetBytes(pw   salt)); 
return Convert.ToBase64String(hash);

I am not sure why this wouldn't work as I'm completely new to php. Can anyone please help?

CodePudding user response：

In php you have salt password, in .net you have pw salt.

That will give different results. Fix by using:

$pw = $extpassword . $salt;

byte[] hash = sha256.ComputeHash(System.Text.Encoding.UTF8.GetBytes(salt   pw));