PHP Drop Down On Change - php

Question

I have a drop down list called courses. When the user chooses a course, I should show him information about the teacher that gives this course. So, on change I need to get the value selected, and show him the results generated from an sql query.
This is my php code:
$sql= "SELECT id, course_period_id from schedule WHERE STUDENT_ID='$_SESSION[student_id]'";
$result=mysql_query($sql);
$options="";
while ($row=mysql_fetch_array($result)) {
$id=$row["id"];
$course_period_id=$row["course_period_id"];
$course= DBGet(DBQuery("SELECT title FROM course_periods WHERE course_period_id='$course_period_id'"));
$options.="<OPTION VALUE=\"$course[1]['TITLE']\">".$course[1]['TITLE'].'</option>';
}
echo '</TD></TR></TABLE>';
echo "<SELECT>
<OPTION VALUE=0>Choose
$options
</SELECT>";
echo '</TD></TR></TABLE>';
I want to use "href", as I created a php file "teachers_info.php" with the following code:
if(!empty($_GET['Course']))
{
$sql="SELECT teacher_id FROM course_periods where title= '$course'";
$teacher_id= DBGet(DBQuery($sql));
$result= DBGet(DBQyery(" SELECT first_name, last_name, phone, email FROM staff WHERE staff_id = '$teacher_id[1]['teacher_id']'"));
echo "<table border='1'>
<tr>
<th>Firstname</th>
<th>Lastname</th>
<th>Phone</th>
<th>E-mail</th>
</tr>";
echo "<tr>";
echo "<td>" . $result[1]['first_name'] . "</td>";
echo "<td>" . $result[1]['last_name'] . "</td>";
echo "<td>" . $result[1]['phone'] . "</td>";
echo "<td>" . $result[1]['email'] . "</td>";
echo "</tr>";
echo "</table>";
}
How can I do this?
Thanks :)

Answer 1

Ok this is a bad approach, for multiple reasons:
This should be done using ajax
Don't use $_SESSION for this
I'll help you out. The first thing you need is jquery. You can find it here: http://jquery.com .
Next take a look at this picture to understand how ajax works:
In short, ajax is used to make calls to the server and update the page with the response without reloading. In your case, you will make a call to the server, send course and receive the results.
Once you have jquery set up, you have to write this:
$(function(){
$("select").on("change", function(){
var value = $(this).value(); //get the selected id
$.get("requesturl.php", {course: value}, function(){
// do something with the response
}, "json");
})
})
The requesturl.php file would look as follows:
$course = $_GET["course"]
if($course){
//execute Database query and store it in $result
echo json_encode($result);
}

Answer 2

you can modify this code.
myform.php
<script type="text/javascript">
$(document).ready(function(){
//Below line will get value of Category and store in id
$("#Category").change(function()
{
var id=$(this).val();
var dataString = 'id='+ id;
$.ajax
({
type: "GET",
url: "Ajax_SubCategory.php",
data: dataString,
cache: false,
success: function(html)
{
//This will get values from Ajax_SubCategory.php and show in Subcategory Select option
$("#SubCategory").html(html);
}
});
});
});
</script>
<form>
<?php
mysql_connect("localhost","root","") or die("error connect");
mysql_select_db("test") or die(" error database");
echo "<select name='Category' id='Category'>";
echo "<option value='' disabled='' selected='' >--Select Category--</option>";
$q6=mysql_query("select DISTINCT Category from category");
while($r6=mysql_fetch_array($q6))
{
echo "<option value='$r6[0]' >$r6[0]</option>";
}
echo "</select>";
echo "<select name='SubCategory' id='SubCategory'>";
echo "<option value='' disabled='' selected='' >--Select Sub Category--</option>";
echo "</select>";
?>
</form>
Ajax_SubCategory.php
<?php
mysql_connect("localhost","root","") or die("error connect");
mysql_select_db("test") or die("error database");
if($_GET['id'])
{
$id=$_GET['id'];
$sql=mysql_query("select SubCategory from category where Category='$id'");
while($row=mysql_fetch_array($sql))
{
$data=$row['SubCategory'];
echo '<option value="'.$data.'">'.$data.'</option>';
//echo "<input type='checkbox' value='".$data."' >".$data.;
}
}
?>

Answer 3

Well if you want the PHP to get something you ned to post something. You either add a submit button or:
echo "<select name=\"course\" id=\"course\" onchange=\"this.form.submit()\">
<OPTION VALUE=0>Choose
$options
</SELECT>";
Then you can utilize if(!empty($_GET['Course'])) {
because $_GET[] need the form to be submited.