<?php
    error_reporting(E_ALL);
    include 'config.php';
           
    $vorname = $_POST['vorname'];
    $name = $_POST['name'];
    $alter = $_POST['alter'];
    $geschlecht = $_POST['geschlecht'];  
    
    @mysql_connect(MYSQL_HOST, MYSQL_USER) OR
        die("Keine Verbindung zur Datenbank. Fehlermeldung:".mysql_error());
    mysql_select_db(MYSQL_DATABASE) OR
        die("Konnte Datenbank nicht benutzen, Fehlermeldung: ".mysql_error());  
        
    $sql = "INSERT INTO member
                       (vorname,
                        name,
                        alter,
                        geschlecht)
                    VALUES
                       ('$vorname',
                        '$name',
                        '$alter',
                        '$geschlecht')";                       
    $result = mysql_query($sql) OR die(mysql_error());     
 ?>

You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near 'alter, geschlecht)