Mysql 5.7 checking user credentials via PHP - php

Question

i am beginner in PHP and MySQL. I am trying validate user inputs (Username and Password) in MySQL 5.7 DB but no chance. Let me explain my problem;
I created a user in firstdb with username: firstuser password: firstpassword via phpMyAdmin page.
CODE (check_user-pass.php)
<?php
ob_start();
$host="localhost"; // Host name
$username="root"; // Mysql username
$password="rootpassword"; // Mysql password
$db_name="firstdb"; // Database name
$tbl_name="mysql.user"; // Table name
$conn = new mysqli($host, $username, $password, $db_name);
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";
// Define $username and $password
$myusername=$_POST['EMail'];
$mypassword=$_POST['Password'];
// To protect MySQL injection (more detail about MySQL injection)
$myusername = mysqli_real_escape_string($conn,$_POST['EMail']);
$mypassword = mysqli_real_escape_string($conn,$_POST['Password']);
$sql="SELECT * FROM $tbl_name WHERE user='$myusername' and authentication_string='$mypassword'";
$result = $conn->query($sql);
$count = 0;
// Mysql_num_row is counting table row
if ($result = mysqli_query($conn, $sql)) {
/* determine number of rows result set */
$count = mysqli_num_rows($result);
printf("Result set has %d rows.\n", $count);
/* close result set */
mysqli_free_result($result);
}
// If result matched $username and $password, table row must be 1 row
if ($count==1) {
echo "Success! $count";
} else {
echo "Unsuccessful! $count";
}
ob_end_flush();
?>
Code return: Connected successfullyResult set has 0 rows. Unsuccessful! 0
If i remove this line: and authentication_string='$mypassword'Code return: Connected successfullyResult set has 1 rows. Success! 1
I succesfully retrieve user inputs from index.php to check_user-pass.php but there is no clear password column in mysql.user table for matching in database.
I search over net and find; password column changed to authentication_string in 5.x but this column carry the hashed thing. So i can't match the user password with this.
Question 1
Should i create a table and store the username and clear password for every user in DB for validating?
Question 2
If question1 answer is NO, how can achieve this validation problem?

Answer 1

I've done so many logins for people I just wrote a class for myself, its on github if you're interested
https://github.com/wazimshizm/secure-login
for easiest out of the box authentication, use this for storing & comparing passwords:
password_hash($passwordVariable, PASSWORD_DEFAULT);
password_verify($inputPassword, $storedPassword);