Basic php/db password encryption - php

Question

've set up two simple php files for a login/register feature on my android app.
I would like to know a simple way to get it to save/write an encrypted password to the mysql database. at the moment its only writing plain text for password.
Code for register.php is :
$username = $_POST["username"];
$email = $_POST["email"];
$password = $_POST["password"];
$statement = mysqli_prepare($con, "INSERT INTO User (username, email, password) VALUES (?, ?, ?)" );
mysqli_stmt_bind_param($statement, "sss", $username, $email, $password);
mysqli_stmt_execute($statement);
mysqli_stmt_close($statement);
mysqli_close($con);
and code for login stuff is:
$password = $_POST["password"];
$username = $_POST["username"];
$statement = mysqli_prepare($con, "SELECT * FROM User WHERE username = ? AND password = ?");
mysqli_stmt_bind_param($statement, "ss", $username, $password);
mysqli_stmt_execute($statement);
mysqli_stmt_store_result($statement);
mysqli_stmt_bind_result($statement, $userID, $username, $email, $password);
$user = array();
while(mysqli_stmt_fetch($statement)) {
$user[username] = $username;
$user[email] = $email;
$user[password] = $password;
}
echo json_encode($user);
mysqli_stmt_close($statement);
mysqli_close($con);
very simple question i know but just learning myself. thanks
EDIT:
Based on Jamesking56's link/ response i've come out with this, but now its not writing to db at all:
$username = $_POST["username"];
$email = $_POST["email"];
$password = $_POST["password"];
$passwordHash = password_hash($password, PASSWORD_DEFAULT);
$statement = mysqli_prepare($con, "INSERT INTO User (username, email, password) VALUES (?, ?, ?)" );
mysqli_stmt_bind_param($statement, "sss", $username, $email, $passwordHash);
mysqli_stmt_execute($statement);
mysqli_stmt_close($statement);
mysqli_close($con);

Answer 1

If you are using PHP 5.5 or newer, there are some built-in functions for password hashing called password_hash() and password_verify().
Never use MD5 or SHA1 on its own for password hashing as they can be reversed by using rainbow tables.
You should use a hashing mechanism with a secret that you define which gives you hashes which are unique to your application. The 'secret' you create should never be shared through VCS.
A good article about this can be found here: http://www.phptherightway.com/#password_hashing
For anyone using PHP versions lower than 5.5 you can use crypt():
http://php.net/manual/en/function.crypt.php
PHP 5.4 will be unsupported as of 14th September 2015 so please consider upgrading to 5.5.