How do I add data from two tables in mySQL and PHP? - php

Question

I have a table with two fields, named credithour and gradepoint.
I want to add the data from each row of credithour with gradepoint.
My code :
$totalcredithour = 0;
$GPA = "SELECT * FROM $dept_stu_id WHERE sessionyear = '$sessionyear'" or die (mysql_error());
$resultGPA = mysql_query($GPA);
while($data = mysql_fetch_array($resultGPA))
{
$credithour = "$data[credithour]";
$gradepoint = "$data[gradepoint]";
echo $totalcredithour += $credithour;
}
What am I doing wrong?
It added data, but showing the first credit hour also besides result.
Suppose, here i entered two data 3 and 5. When I run this code it echo 38. Which means "3+5=8" and 1st credithour = "3".

Answer 1

Actually other answer are wrong, you're doing or die(mysql_error()); next to a string, that's not right.
Your code should be like this..
$totalcredithour = 0;
$GPA = "SELECT * FROM `".$dept_stu_id."` WHERE sessionyear = `".$sessionyear."` ";
$resultGPA = mysql_query($GPA) or die(mysql_error());
while($data = mysql_fetch_array($resultGPA, MYSQL_ASSOC))
{
$credithour = $data['credithour'];
$gradepoint = $data['gradepoint'];
echo $totalcredithour += $credithour; //Make sure `$totalcredithot` isn't null/doesn't exist.
}

Answer 2

try something like this in your while loop:
$credithour = $data['credithour'];
$gradepoint = $data['gradepoint'];

Answer 3

Try it like this
I have edited the answer and added the floatval function
$totalcredithour = 0;
$GPA = "SELECT * FROM `".$dept_stu_id."` WHERE sessionyear = '".$sessionyear."'" or die (mysql_error());
$resultGPA = mysql_query($GPA);
while($data = mysql_fetch_array($resultGPA))
{
$credithour = $data['credithour'];
$gradepoint = $data['gradepoint'];
echo $totalcredithour += floatval($credithour);
}