&lt;?php
    $mail = filter_var($_POST[&#39;mail&#39;], FILTER_VALIDATE_EMAIL);
    $pass = $_POST[&#39;pass&#39;];
    $name = $_POST[&#39;name&#39;];
    $surname = $_POST[&#39;surname&#39;];
    $gender = $_POST[&#39;gender&#39;];

    if(!$mail) {
        die(&#39;Invalid email!&#39;);
    }

    if(strlen($pass) &lt; 8) {
        die(&#39;Password too short!&#39;);
    }

    if(!$name || !$surname) {
        die(&#39;Invalid user data!&#39;);
    }

    $data = $mail . &#39; &#39; . $pass . &#39; &#39; . $name . &#39; &#39; . $surname . &#39; &#39; . $gender . &quot;n&quot;; 

    file_put_contents(&#39;users.txt&#39;, $data, FILE_APPEND);

    echo &#39;Data saved&#39;;
?&gt;