User submits username from p1.html, p2.php does the authorization work with db.php as required file and upon successful authorization, it directs the user to p3.php.
I am noticing strange behavior or may be I am making some mistake and not able to identify it right now.
Case 1 with No Errors:
When I comment out the line print "self.location='p3.php';"; in p2.php, my control after form submission is going to halt at db.php. And hence, I can see the username getting printed by the following line in db.php.
echo"Test for db user variable in databaseconn.php:";
var_dump($user);
p1.html
<form method="post" action= "p2.php" name="lform">
<span class="style1">User Name :</span>
<input type="text" name="user" size="25">
<input type="submit" value="login">
</form>
p2.php
<?php
session_start();
$user = $_POST["user"];
$_SESSION['username'] = $user;
require('../myDBFolder/db.php');
$sql="SELECT * FROM $table_name_users WHERE username = \"$user\"";
$result=mysqli_query($connection,$sql) or trigger_error("Couldn't Execute Query in page2.php: ". mysqli_error($sql));
$num = mysqli_num_rows($result);
if ($num != 0) {
print "<script>";
print "self.location='p3.php';";
print "</script>";
} else {
echo "<p>you're not authorized";
}
?>
p3.php
<?php
session_start();
require('../myDBFolder/db.php');
$user = $_SESSION['username'];
$sql = "SELECT * FROM $table_name_data WHERE username = '$user'";
$result = mysqli_query($connection,$sql) or trigger_error("Could Not Execute the Query ! : ". mysqli_error($connection));
?>
db.php
<?php
$db_server = "localhost";
$db_name = "PracticeDB";
$db_user = $user; // This is Line #21 from the error log for Undefined User variable
$table_name_data = "collegestudents";
echo"Test for db user variable in databaseconn.php:";
var_dump($user);
$connection = mysqli_connect($db_server,$db_user) or trigger_error("Could Not Connect to the Database : ". mysqli_connect_error(), E_USER_ERROR);
$db = mysqli_select_db($connection,$db_name) or trigger_error("Could Not Select the Database : " . $db_name . ':' .mysqli_error($connection));
?>