i have tried this code to insert value into database, but i don't Know why, the value was not send into the databases. The table i have created in the mysql :
    <?php
    require_once "connection.php";
        $conn = connect();
        $db = connectdb();
    mysql_select_db($db,$conn) or die (mysql_error() . "\n");
    $query_usr = "select * from soalselidik";
    $usr = mysql_query($query_usr,$conn) or die(mysql_error()."\n".$query_usr);
    $row_usr=mysql_fetch_assoc($usr);
//to insert in database
    $a1=$_POST['a1'];
    $a2=$_POST['a2'];
    $a3=$_POST['a3'];
    $a4=$_POST['a4'];
    $b1=$_POST['b1'];
    $b2=$_POST['b2'];
    $b3=$_POST['b3'];
    $b4=$_POST['b4'];
    $c1=$_POST['c1'];
    $c2=$_POST['c2'];
    $c3=$_POST['c3'];
    $c4=$_POST['c4'];
    $d1=$_POST['d1'];
    $d2=$_POST['d2'];
    $d3=$_POST['d3'];
    $d4=$_POST['d4'];
    $e1=$_POST['e1'];
    $f1=$_POST['f1'];
    echo $query ="insert into soalselidik (a1,a2,a3,a4,b1,b2,b3,b4,c1,c2,c3,c4,d1,d2,d3,d4,e1,f1) values('$a1','$a2','$a3','$a4','$b1','$b2','$b3','$b4','$c1','$c2','$c3','$c4''$d1','$d2','$d3','$d4','$e1','$f1')";
    $result = mysql_query($query);
    echo "<script languange = 'Javascript'>
                    alert('thankyou ! Penilaian anda diterima ');
                    location.href = 'home.php';</script>";
    ?> 
 
     
    