use session username as "WHERE" in mysqli query [closed] - php

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I know I am doing something wrong but I really would like to know what it is. I can echo the
username of the session loggedin user using <?php echo $_SESSION['username']; ?>but I don't know why it doesn't work when I try to query database using the same technique. my codes below
I include this in the page
<?php
session_start();
$username=$_SESSION['username'];
?>
and here is the code that was suppose to display firstname and user_id of the sessions logged in user
<?php
$conn = new mysqli('localhost', 'root', 'browser', 'test');
if (mysqli_connect_errno()) {
exit('Connect failed: '. mysqli_connect_error());
}
$username = '$username';
$sql = "SELECT `user_id`, `firstname` FROM `members` WHERE `username`='$username'";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
while($row = $result->fetch_assoc()) {
echo '<br /> user_id: '. $row['user_id']. ' - firstname: '. $row['firstname'];
}
}
else {
echo '0 results';
}
$conn->close();
?>

Answer 1

$username = '$username';
PHP variables inside single-quotes are not expanded. So now your variable is the literal string '$username', which undoubtedly won't match any user in your database.
You probably need to set $username = $_SESSION['username']; in your second PHP script.