i'm a beginner

i get this error

Parse error: syntax error, unexpected '"idnumber"' (T\_CONSTANT\_ENCAPSED\_STRING) in /storage/h6/783/918783/public\_html/add\_student\_info.php on line 8

this is my code--->>

```
    <?php

    $host = "mmsis.000webhostapp.com";
    $user = "id918783_mdb";
    $password = "";
    $db = "id918783_mmsisdb";

    $id_number = $_POST"idnumber";
    $first_name = $_POST"firstname";
    $middle_name = $_POST"middlename";
    $last_name = $_POST"lastname";
    $course = $_POST"course";
    $password = $_POST"password";
    $confirm_password = $_POST"confirmpassword";
    $barangay = $_POST"barangay";
    $zip_code = $_POST"zipcode";

    $query = "insert into tblStudentInfo values ('$first_name','$middle_name','$last_name','$course','$password','$confirm_password','$barangay','$zip_code'); ";

    mysqli_query(mysqli_connect($host,$user,$password,$db),$query)
    ?>

```

what might be the problem??please help