表单输入不会显示在mysql中

Question

When I submit the following code, the only thing that goes into my database is the second select section (49/43). The other inputs are written into the database with the value "0", no matter what input I submit. I would be very grateful for some help!

<?php 
if ( ! empty( $_POST ) ) {

    $mysqli = new mysqli( 'localhost', 'XXX', 'XXX', 'XXX' );

    if ( $mysqli->connect_error ) {
        die( 'Connect Error: ' . $mysqli->connect_errno . ': ' . $mysqli->connect_error );
    }

    $sql = "INSERT INTO user ( sex, pre, nmbr) VALUES ( '{$mysqli->real_escape_string($_POST['sex'])}', '{$mysqli->real_escape_string($_POST['pre'])}', '{$mysqli->real_escape_string($_POST['nmbr'])}' )";
    $insert = $mysqli->query($sql);

    if ( $insert ) {
        echo "Sucess!";
    } else {
        die("Error: {$mysqli->errno} : {$mysqli_error}");
    }

    $mysqli->close();
}

?>

<form method="post" action="">
        <select name="sex">
            <option>W</option>
            <option>M</option>
        </select>
        <select name="pre">
          <option>+49</option>
          <option>+43</option>
         </select>

        <input name"nmbr" type="text" placeholder=" Deine Handynummer hier eingeben">
        <button> <i class="fa fa-arrow-right"></i></button>
    </form>

Answer 1

With the help of the comment section, this works just fine now.

Additional info: The column types in the database are VARCHAR for "sex" and "pre" as well as INT for the "nmbr" input. Another sidenote from the comment section: "since you're obviously using everything inside the same file, you need to use isset() and/or !empty() against all your POST arrays."

<?php 
if ( ! empty( $_POST ) ) {



    $mysqli = new mysqli( 'localhost', 'XXX', 'XXX', 'XXX' );

    if ( $mysqli->connect_error ) {
        die( 'Connect Error: ' . $mysqli->connect_errno . ': ' . $mysqli->connect_error );
    }

    $sql = "INSERT INTO user ( sex, pre, nmbr) VALUES ( '{$mysqli->real_escape_string($_POST['sex'])}', '{$mysqli->real_escape_string($_POST['pre'])}', '{$mysqli->real_escape_string($_POST['nmbr'])}' )";
    $insert = $mysqli->query($sql);

    if ( $insert ) {
        echo "Success!";

    } else {
        die("Error: {$mysqli->errno} : {$mysqli_error}");
    }

    $mysqli->close();
}

?>

<form method="post" action="">
        <select name="sex">
            <option>W</option>
            <option>M</option>
        </select>
        <select name="pre">
          <option>+49</option>
          <option>+43</option>
         </select>

        <input name="nmbr" type="text" placeholder=" Deine Handynummer hier eingeben">
        <button> <i class="fa fa-arrow-right"></i></button>
    </form>