Task: SQL-based authentication
Go: package main

import (
    "bytes"
    "crypto/md5"
    "crypto/rand"
    "database/sql"
    "fmt"

    _ "github.com/go-sql-driver/mysql"
)

func connectDB() (*sql.DB, error) {
    return sql.Open("mysql", "rosetta:code@/rc")
}

func createUser(db *sql.DB, user, pwd string) error {
    salt := make([]byte, 16)
    rand.Reader.Read(salt)
    _, err := db.Exec(`insert into users (username, pass_salt, pass_md5)
        values (?, ?, ?)`, user, salt, saltHash(salt, pwd))
    if err != nil {
        return fmt.Errorf("User %s already exits", user)
    }
    return nil
}

func authenticateUser(db *sql.DB, user, pwd string) error {
    var salt, hash []byte
    row := db.QueryRow(`select pass_salt, pass_md5 from users
        where username=?`, user)
    if err := row.Scan(&salt, &hash); err != nil {
        return fmt.Errorf("User %s unknown", user)
    }
    if !bytes.Equal(saltHash(salt, pwd), hash) {
        return fmt.Errorf("User %s invalid password", user)
    }
    return nil
}

func saltHash(salt []byte, pwd string) []byte {
    h := md5.New()
    h.Write(salt)
    h.Write([]byte(pwd))
    return h.Sum(nil)
}

func main() {
    
    db, err := connectDB()
    defer db.Close()
    createUser(db, "sam", "123")
    err = authenticateUser(db, "sam", "123")
    if err == nil {
        fmt.Println("User sam authenticated")
    }

    
    fmt.Println()
    
    rows, _ := db.Query(`select username, pass_salt, pass_md5 from users`)
    var user string
    var salt, hash []byte
    for rows.Next() {
        rows.Scan(&user, &salt, &hash)
        fmt.Printf("%s %x %x\n", user, salt, hash)
    }
    
    err = createUser(db, "sam", "123")
    fmt.Println(err)
    
    err = authenticateUser(db, "pam", "123")
    fmt.Println(err)
    
    err = authenticateUser(db, "sam", "1234")
    fmt.Println(err)
    
    db.Exec(`truncate table users`)
}

PHP: function connect_db($database, $db_user, $db_password, $host = 'localhost', $port = NULL, $die = false) {





	if(!$db_handle = @mysql_connect($host.($port ? ':'.$port : ''), $db_user, $db_password)) {
		if($die)
			die("Can't connect to MySQL server:\r\n".mysql_error());
		else
			return false;
	}
	if(!@mysql_select_db($database, $db_handle)) {
		if($die)
			die("Can't select database '$database':\r\n".mysql_error());
		else
			return false;
	}
	return $db_handle;
}

function create_user($username, $password, $db_handle) {


	if(strlen($username) > 32)
		return false;

	$salt = '';
	do {
		$salt .= chr(mt_rand(32, 254));
	} while(strlen($salt) < 16);

	$pass_md5 = md5($salt.$password);

	$username = mysql_real_escape_string($username);
	$salt = mysql_real_escape_string($salt);

	if(!@mysql_query("INSERT INTO users (username,pass_salt,pass_md5) VALUES('$username','$salt','$pass_md5')", $db_handle))
		return false;

	return mysql_insert_id($db_handle);
}

function authenticate_user($username, $password, $db_handle) {



	$safe_username = mysql_real_escape_string($username);

	if(!$result = @mysql_query("SELECT * FROM users WHERE username='$safe_username'", $db_handle))
		return false;

	$row = @mysql_fetch_assoc($result);

	if(md5($row['pass_salt'].$password) != $row['pass_md5'])
		return false;

	return $row['userid'];
}