如何将多个选择值插入数据库？

Question

I want to select multiple choice and insert the values in database. How can I do this?

     <select name="instructor" multiple>
      <option value="9000">Zaher</option>
      <option value="9001">Samih</option>
      <option value="9010">Majd</option>
     <select>

    $instructor=$_GET['instructor'];
    if(isset($_SESSION['courses']) && isset($_SESSION['semester'])){

       $coursechosen= $_SESSION['courses'];
        $semesterchosen=$_SESSION['semester'];
    $query="Insert INTO coordinators(instructor_id,course_code,semester) 
    VALUES ('$instructor','$coursechosen','$semesterchosen')";

    mysql_query($query);
    }

Answer 1

<select name="instructor[]" multiple>
      <option value="9000">Zaher</option>
      <option value="9001">Samih</option>
      <option value="9010">Majd</option>
     <select>

// Your PHP code
<?php
foreach ($_GET['instructor'] as $value) {
            $instructor.= $value.", ";
        }

    if(isset($_SESSION['courses']) && isset($_SESSION['semester'])){

       $coursechosen= $_SESSION['courses'];
        $semesterchosen=$_SESSION['semester'];
    $query="Insert INTO coordinators(instructor_id,course_code,semester) 
    VALUES ('$instructor','$coursechosen','$semesterchosen')";

    mysql_query($query);
    }
?>

Answer 2

<select name="instructor[]" multiple>
<?php 
foreach ($_POST['instructor'] as $icon) 
{
 ///your insert code//


}?>

Answer 3

        <select name="instructor[]" multiple>
              <option value="9000">Zaher</option>
              <option value="9001">Samih</option>
              <option value="9010">Majd</option>
             <select>
                <input type="submit" value="send" name="send">
         
       //php code
        <?php
        if (isset($_POST['send']))
    {
        if (isset($_POST['instructor']))
        {
            $instructor= implode(',',$_POST['instructor']);
            $query="INSERT INTO `database` VALUES ('0','$instructor')";

mysql_query($query);
        }
        else
        {
            print "no selected";
        }
    }
        
        ?>